Analytical and Bioanalytical Chemistry (v.408, #14)

Nanocrystalline diamond sensor targeted for selective CRP detection: an ATR-FTIR spectroscopy study by Per Ola Andersson; Pernilla Viberg; Pontus Forsberg; Fredrik Nikolajeff; Lars Österlund; Mikael Karlsson (3675-3680).
Protein immobilization on functionalized fluorine-terminated nanocrystalline (NCD) films was studied by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy using an immobilization protocol developed to specifically bind C-reactive protein (CRP). Using an ATR-FTIR spectroscopy method employing a force-controlled anvil-type configuration, three critical steps of the ex situ CRP immobilization were analyzed. First, the NCD surface was passivated by deposition of a copolymer layer consisting of polyethylene oxide and polypropylene oxide. Second, a synthetic modified polypeptide binder with high affinity to CRP was covalently attached to the polymeric film. Third, CRP dissolved in aqueous buffer in concentrations of 10–20 μg/mL was added on the functionalized NCD surface. Both the amide I and II bands, due to the polypeptide binder and CRP, were clearly observed in ATR-FTIR spectra. CRP amide I bands were extracted from difference spectra and yielded bands that agreed well with the reported amide I band of free (non-bonded) CRP in solution. Thus, our results show that CRP retains its secondary structure when it is attached to the polypeptide binders. Compared to previous IR studies of CRP in solution, about 200 times lower concentration was applied in the present study. Graphical Abstract Direct non-destructive ATR-FTIR analysis of C-reactive protein (CRP) selectively bound to functionalized nanocrystalline diamond (NCD) sensor surface
Keywords: Infrared spectroscopy; ATR-FTIR; Nanocrystalline diamond; CRP; Protein binders; Biosensor

Development and application of a QuEChERS-based extraction method for the analysis of 55 pesticides in the bivalve Scrobicularia plana by GC-MS/MS by Catarina Cruzeiro; Nádia Rodrigues-Oliveira; Susana Velhote; Miguel Ângelo Pardal; Eduardo Rocha; Maria João Rocha (3681-3698).
A method for quantitative determination of 55 pesticides in a bivalve matrix was established, based on QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) extraction and using gas chromatography (GC)-ion trap (IT) mass spectrometry (MS/MS). Accomplishing the European SANCO guidelines, this method was validated using 5 g of homogenized soft tissue, allowing the quantification of pesticides at ng/g of wet weight (ww). Quantification limits and recovery rates ranged from 0.33 to 10.3 μg/L and from 78 to 119 %, respectively. As an important mollusc, not only from an ecological perspective but also for food consumption, the peppery furrow shell (Scrobicularia plana) was sampled at three strategical sites (Ria Formosa Lagoon, in the south of Portugal) during 2012–2013, over six campaigns. A total of 2160 animals were pooled by place and sex. No statistical differences were found among sites or between sexes. Forty percent of the sampled pools were above quantification limits, reaching total annual average concentrations of ∑800 ng/g ww. Additionally, 83 % of the selected compounds showed concentrations above the legal limits set by the European Directive 2013/39/EU. In conclusion, the applied method was successful and proved that bivalves were contaminated by the selected pesticides. In future work, this methodology can be used to monitor body burdens and obtain data for predicting impacts in shellfish consumers. Graphical Abstract Resume of pesticides extraction and analyses process from S. plana
Keywords: 2013/39/EU; Fungicides; Herbicides; Insecticides; SANCO/825/00; Seafood

An ascorbic acid sensor based on cadmium sulphide quantum dots by Manjunatha Ganiga; Jobin Cyriac (3699-3706).
We present a Förster resonance energy transfer (FRET)-based fluorescence detection of vitamin C [ascorbic acid (AA)] using cadmium sulphide quantum dots (CdS QDs) and diphenylcarbazide (DPC). Initially, DPC was converted to diphenylcarbadiazone (DPCD) in the presence of CdS QDs to form QD–DPCD. This enabled excited-state energy transfer from the QDs to DPCD, which led to the fluorescence quenching of QDs. The QD–DPCD solution was used as the sensor solution. In the presence of AA, DPCD was converted back to DPC, resulting in the fluorescence recovery of CdS QDs. This fluorescence recovery can be used to detect and quantify AA. Dynamic range and detection limit of this sensing system were found to be 60–300 nM and 2 nM, respectively. We also performed fluorescence lifetime analyses to confirm existence of FRET. Finally, the sensor responded with equal accuracy to actual samples such as orange juice and vitamin C tablets. Graphical abstract Schematic showing the FRET based fluorescence detection of ascorbic acid
Keywords: Förster resonance energy transfer (FRET); Ascorbic acid; Vitamin C; Fluorescence sensor

2-Alkylcyclobutanones (2-ACBs) are uniquely formed when triglycerides-containing food products are exposed to ionizing radiation. Thus, 2-ACBs have been used as marker molecules to identify irradiated food. Most methods to determine 2-ACBs involve mass spectrometric detection after chromatographic separation. The spectrofluorometer is rarely used to determine 2-ACBs because these molecules do not fluoresce. In this study, we developed an ultra-performance liquid chromatography (UPLC) method to determine 2-ACBs. 2-ACBs were converted into fluorophores after reacting with 1-naphthalenyl hydrazine to facilitate their sensitive and selective detection using a fluorescence detector (FLD). Analysis of 2-ACBs using our developed UPLC-FLD method allows sensitive determination of 2-ACBs at a detection limit of 2 ng 2-ACBs per g of fat (30 pg/injection), which is significantly lower than that of existing analytical methods. After validation for trueness and precision, the method was applied to γ-irradiated chicken samples to determine their 2-ACB content. Comparative studies employing liquid chromatography-tandem mass spectrometric method revealed no systematic difference between the two methods, thereby demonstrating that the proposed UPLC-FLD method can be suitably used to determine 2-ACBs in irradiated foodstuffs. Graphical Abstract Determination of radiation-induced food-borne 2-dodecylcyclobutanone and 2-tetradecylcyclobutanone by combining 1-naphthalenyl hydrazine derivatization and ultra-performance liquid chromatography with fluorescence detection
Keywords: 2-Alkylcyclobutanones; Irradiated food; Ultra-performance liquid chromatography; Fluorescence; Precolumn derivatization

Fast detection of coliform bacteria by means of gas chromatography-differential mobility spectrometry by Lena Ganda Saptalena; Andriy Kuklya; Ursula Telgheder (3715-3725).
In this study, we demonstrate that the combination of an enzymatic method (based on Colilert-18 medium) and gas chromatography-differential mobility spectrometry (GC-DMS) can reduce the time required for detection of coliform bacteria (including Escherichia coli) from 18 to 2.5 h. The presented method includes the incubation (~2.5 h) of the sample containing coliform bacteria in Colilert-18 medium. The incubation time of 2.5 h is required for the activation of the β-galactosidase enzyme. Produced during the incubation biomarker o-nitrophenol (ONP) can be detected by means of GC-DMS within just 200 s. The detection limit for ONP was 45 ng (on-column). The method developed in this work provides significantly shorter analysis time compared with standard methods, and can be potentially adapted to the field conditions. Therefore, this method is a promising tool for an early detection of coliform bacteria (including E. coli). Graphical Abstract Fast detection of coliform bacteria by means of GC-DMS
Keywords: Escherichia coli (E. coli); Coliform bacteria; Differential mobility mpectrometry (DMS); MicroAnalyzer; Bacteria detection; Enzymatic method

In the present research, the ZnO-CuO nanoplate composite (ZCNC), solid-phase microextraction (SPME) fiber coating, was prepared and its extraction capability for certain chlorophenols (CPs) was studied through directly sampling the typical CPs mixed standard solution of 4-chlorophenol, 2,3-dichlorophenol, 2,5-dichlorophenol, and 2,4,6-trichlorophenol with high performance liquid chromatography. ZCNC thickness was in the range of 50–65 nm. The effective variables on ZCNC-SPME extraction efficiency were extraction time, salt percentage, and desorption time. Accordingly, a multivariate strategy was applied based on an experimental design by using central composite design for optimizing the significant factors affecting the extraction efficiency. The detection limit and relative standard deviation (RSD) (n = 6), that include repeatability and reproducibility as the target analytes, were in the range of 0.5–5 ng ml−1 and 5.1–14 % of standard solutions at 50 ng ml−1 concentration of CPs, respectively. The developed technique is believed to be successfully applicable to preconcentration and determination of target analytes in environmental water and tomato juice samples. Graphical Abstract Application of zinc oxide-copper oxide nanoplates composite for extraction of chlorophenols in water and tomato juice samples and optimizing condition by experimental design method
Keywords: Chlorophenols; High performance liquid chromatography; Chemometric design; Solid phase microextraction; ZnO-CuO nanoplate

Ultra-rapid targeted analysis of 40 drugs of abuse in oral fluid by LC-MS/MS using carbon-13 isotopes of methamphetamine and MDMA to reduce detector saturation by Matthew Di Rago; Mark Chu; Luke N Rodda; Elizabeth Jenkins; Alex Kotsos; Dimitri Gerostamoulos (3737-3749).
The number of oral fluid samples collected by the road policing authority in Victoria, Australia, requiring confirmatory laboratory analysis for drugs proscribed under Victorian legislation (methamphetamine, MDMA and Δ9-tetrahydrocannabinol) has greatly increased in recent years, driving the need for improved analysis techniques to enable expedient results. The aim of this study was to develop an LC-MS/MS-based targeted oral fluid screening technique that covers a broad range of basic and neutral drugs of abuse that can satisfy increased caseload while monitoring other compounds of interest for epidemiological purposes. By combining small sample volume, simple extraction procedure, rapid LC-MS/MS analysis and automated data processing, 40 drugs of abuse including amphetamines, benzodiazepines, cocaine and major metabolites, opioids, cannabinoids and some designer stimulants were separated over 5 min (with an additional 0.5 min re-equilibration time). The analytes were detected using a Sciex® API 4500 Q-Trap LC-MS/MS system with positive ESI in MRM mode monitoring three transitions per analyte. The method was fully validated in accordance with international guidelines and also monitored carbon-13 isotopes of MDMA and MA to reduce detector saturation effects, allowing for confirmation of large concentrations of these compounds without the need for dilution or re-analysis. The described assay has been successfully used for analysis of oral fluid collected as part of law enforcement procedures at the roadside in Victoria, providing forensic results as well as epidemiological prevalence in the population tested. The fast and reliable detection of a broad range of drugs and subsequent automated data processing gives the opportunity for high throughput and fast turnaround times for forensic toxicology.
Keywords: Oral fluid; LC-MS/MS; Drugs of abuse; Drugs and driving; Carbon-13

A novel four-dimensional analytical approach for analysis of complex samples by Susanne Stephan; Cornelia Jakob; Jörg Hippler; Oliver J. Schmitz (3751-3759).
A two-dimensional LC (2D-LC) method, based on the work of Erni and Frei in 1978, was developed and coupled to an ion mobility-high-resolution mass spectrometer (IM-MS), which enabled the separation of complex samples in four dimensions (2D-LC, ion mobility spectrometry (IMS), and mass spectrometry (MS)). This approach works as a continuous multiheart-cutting LC system, using a long modulation time of 4 min, which allows the complete transfer of most of the first - dimension peaks to the second - dimension column without fractionation, in comparison to comprehensive two-dimensional liquid chromatography. Hence, each compound delivers only one peak in the second dimension, which simplifies the data handling even when ion mobility spectrometry as a third and mass spectrometry as a fourth dimension are introduced. The analysis of a plant extract from Ginkgo biloba shows the separation power of this four-dimensional separation method with a calculated total peak capacity of more than 8700. Furthermore, the advantage of ion mobility for characterizing unknown compounds by their collision cross section (CCS) and accurate mass in a non-target approach is shown for different matrices like plant extracts and coffee. Graphical abstract Principle of the four-dimensional separation
Keywords: 2D-LC; CCS; Ginkgo biloba ; IM-qTOF-MS; Ion mobility; LC+LC

Proteolytic degradation and deactivation of amphibian skin peptides obtained by electrical stimulation of their dorsal glands by Tatiana Yu. Samgina; Miriam I. Tolpina; Elias Hakalehto; Konstantin A. Artemenko; Jonas Bergquist; Albert T. Lebedev (3761-3768).
Amphibians are among the oldest creatures on our planet. Their only defensive weapon efficient against microorganisms and predators involves their skin secretion. The wide range of biological activities of the peptides in the skin secretion of amphibians makes these compounds rather interesting for generation of prospective pharmaceuticals. The first step in studying these molecules requires their structures to be established. Mass spectrometry is the most powerful tool for this purpose. The sampling and sample preparation stages preceding mass spectrometry experiments appear to be rather crucial. The results obtained here demonstrate that these preparation procedures might lead to partial or complete loss of the bioactive peptides in the secretion. Five minutes in water was enough to completely destroy all of the bioactive peptides in the skin secretion of the marsh frog (Rana ridibunda); even immediate addition of methanol to the water solution of the peptides did not prevent partial destruction. Concerted effort should be directed towards development of the most efficient procedure to keep the secreted peptides intact. Graphical Abstract ᅟ
Keywords: Electrical stimulation; Whole-skin extraction; Frog skin peptides; Proteolytic peptides; Orbitrap mass spectrometry; Peptidomics

Multigrid MALDI mass spectrometry imaging (mMALDI MSI) by Annett Urbanek; Stefan Hölzer; Katrin Knop; Ulrich S. Schubert; Ferdinand von Eggeling (3769-3781).
Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) is an important technique for the spatially resolved molecular analysis of tissue sections. The selection of matrices influences the resulting mass spectra to a high degree. For extensive and simultaneous analysis, the application of different matrices to one tissue sample is desirable. To date, only a single matrix could be applied to a tissue section per experiment. However, repetitive removal of the matrix makes this approach time-consuming and damaging to tissue samples. To overcome these drawbacks, we developed a multigrid MALDI MSI technique (mMALDI MSI) that relies on automated inkjet printing to place differing matrices onto predefined dot grids. We used a cooled printhead to prevent cavitation of low viscosity solvents in the printhead nozzle. Improved spatial resolution of the dot grids was achieved by using a triple-pulse procedure that reduced droplet volume. The matrices can either be applied directly to the thaw-mounted tissue sample or by precoating the slide followed by mounting of the tissue sample. During the MALDI imaging process, we were able to precisely target different matrix point grids with the laser to simultaneously produce distinct mass spectra. Unlike the standard method, the prespotting approach optimizes the spectra quality, avoids analyte delocalization, and enables subsequent hematoxylin and eosin (H&E) staining. Graphical Abstract Scheme of the pre-spotted multigrid MALDI MSI workflow
Keywords: Mass spectrometry imaging; Inkjet printing; Simultaneous analysis; Sub-pixel; Multiplex; Multigrid

Fast analysis of caffeine in beverages and drugs by paper spray tandem mass spectrometry by Domenico Taverna; Leonardo Di Donna; Lucia Bartella; Anna Napoli; Giovanni Sindona; Fabio Mazzotti (3783-3787).
A simple and fast method based on paper spray mass spectrometry for the determination of caffeine in commercial beverages and drugs has been developed; the analyses were carried out in MRM mode, monitoring the transitions m/z 195 → m/z 138 for caffeine and m/z 198 → m/z 140 for the labeled internal standard. To verify the reliability of the proposed approach, a spiked sample (soda drink and paracetamol tablet) with a known amount of caffeine has been prepared and analyzed by PS-MS, providing accuracy values about 100 %; the LOQ and LOD values were calculated at 1.2 and 1.6 μg/mL, respectively. Both beverages and drugs were also analyzed with the classic analytical method based on LC-UV measurements, showing consistent results between the two approaches, thus confirming the reliability of the developed ambient MS determination. Graphical Abstract The assay of caffeine by paper mass spectrometry
Keywords: Caffeine; Paper spray; Mass spectrometry; Multiple reaction monitoring; Quantitative assay

Wine taste balance evolves during oak aging by the release of volatile and non-volatile compounds from wood. Among them, an enantiomer of lyoniresinol, (+)-lyoniresinol, has been shown to exhibit bitterness. To evaluate the impact of (+)-lyoniresinol on wine taste, a two-step quantitation method was developed and validated. First, (±)-lyoniresinol was assayed in wines, spirits, and oak wood macerates by C-18 liquid chromatography-high resolution mass spectrometry (LC-HRMS). Then, the lyoniresinol enantiomeric ratio was determined by chiral LC-HRMS in order to calculate the (+)-lyoniresinol content. In red and white wines, the average concentrations of (+)-lyoniresinol were 1.9 and 0.8 mg/L, respectively. The enantiomer proportions were not affected by bottle aging, and lyoniresinol appeared to remain stable over time. The sensory study of (+)-lyoniresinol established its perception threshold at 0.46 mg/L in wine. All the commercial wines quantitated were above this perception threshold, demonstrating its impact on wine taste by an increase in bitterness. In spirits, (+)-lyoniresinol ranged from 2.0 to 10.0 mg/L and was found to be released continuously during oak aging. Finally, neither botanical origin nor toasting was found to significantly affect the (+)-lyoniresinol content of oak wood. Graphical abstract From oak wood to wine: evaluation of the influence of (+)-lyoniresinol on the bitterness of wines and spirits
Keywords: Lignan; Chiral separation; Bitterness; Orbitrap mass spectrometry; Taste-active compounds; Oak aging

A rapid and sensitive method for kinetic study and activity assay of DNase I in vitro based on a GO-quenched hairpin probe by Wei Xu; Zhenhua Xie; Chunyi Tong; Lan Peng; Changhui Xiao; Xuanming Liu; Yonghua Zhu; Bin Liu (3801-3809).
As a waste-management endonuclease, DNase I has been suggested to be one of the deoxyribonucleases responsible for DNA fragmentation during apoptosis. We report here an alternative fluorescence method for DNase I assay with high accuracy and sensitivity by applying a DNA/GO (graphene oxide) probe. The method with a detection limit of 1 U mL–1 was then applied to investigate the effects of external factors including antibiotics and heavy metal ions on DNase I. The results demonstrated that gentamicin sulfate was a strong inhibitor with an IC50 value of 0.57 ± 0.12 mM. The investigated heavy metal ions showed an inhibitory effect on DNase I activity in a concentration dependent manner with IC50 values of 0.04 μg/mL (Hg2+), 0.10 μg/mL (Pb2+), 1.35 μg/mL (Cd2+), 1.20 μg/mL (As2+), and 1.80 μg/mL (Cu2+). Finally, the new method was applied to detect DNase levels in complicated tumor tissue and cell samples and the results showed that DNase levels increased in tumor tissues compared with that of adjacent tissue. From the above results, we conclude that the method can be widely used for high - throughput assay of DNase I in biological samples as well as drug screening in vitro. Graphical Abstract The schematic of real-time monitoring of DNase I using GO - quenched hairpin probe as the substrate. The process of nucleotide digestion catalyzed by DNase I produces short fragments of hairpin probe and accordingly causes a significant increase in fluorescence. At first, GO can absorb the hairpin probes and quenched their fluorescence. When there is DNase I, the DNase can cleave the double strands of DNA. Fluorescence is restored due to the significantly weaker binding ability of small DNA fragments to GO compared with long DNA fragments. So, we can detect the increase in fluorescence to study the activity of DNase.
Keywords: DNase I; Graphene oxide; Hairpin probe; Real time; Tumor

Fluorescent biosensor for the detection of hyaluronidase: intensity-based ratiometric sensing and fluorescence lifetime-based sensing using a long lifetime azadioxatriangulenium (ADOTA) fluorophore by Rahul Chib; Mark Mummert; Ilkay Bora; Bo W. Laursen; Sunil Shah; Robert Pendry; Ignacy Gryczynski; Julian Borejdo; Zygmunt Gryczynski; Rafal Fudala (3811-3821).
In this report, we have designed a rapid and sensitive, intensity-based ratiometric sensing as well as lifetime-based sensing probe for the detection of hyaluronidase activity. Hyaluronidase expression is known to be upregulated in various pathological conditions. We have developed a fluorescent probe by heavy labeling of hyaluronic acid with a new orange/red-emitting organic azadioxatriangulenium (ADOTA) fluorophore, which exhibits a long fluorescence lifetime (∼20 ns). The ADOTA fluorophore in water has a peak fluorescence lifetime of ∼20 ns and emission spectra centered at 560 nm. The heavily ADOTA-labeled hyaluronic acid (HA-ADOTA) shows a red shift in the peak emission wavelength (605 nm), a weak fluorescence signal, and a shorter fluorescence lifetime (∼4 ns) due to efficient self-quenching and formation of aggregates. In the presence of hyaluronidase, the brightness and fluorescence lifetime of the sample increase with a blue shift in the peak emission to its original wavelength at 560 nm. The ratio of the fluorescence intensity of the HA-ADOTA probe at 560 and 605 nm can be used as the sensing method for the detection of hyaluronidase. The cleavage of the hyaluronic acid macromolecule reduces the energy migration between ADOTA molecules, as well as the degree of self-quenching and aggregation. This probe can be efficiently used for both intensity-based ratiometric sensing as well as fluorescence lifetime-based sensing of hyaluronidase. The proposed method makes it a rapid and sensitive assay, useful for analyzing levels of hyaluronidase in relevant clinical samples like urine or plasma. Graphical Abstract Scheme showing cleavage of HA-ADOTA probe by hyaluronidase and the change in the emission spectrum of HA-ADOTA probe before and after cleavage by hyaluronidase
Keywords: Hyaluronidase sensing; Azadioxatriangulenium fluorophore; Ratiometric sensing; Fluorescence lifetime-based sensing; Fluorescence-based assay

A novel aptasensor labeled with Mn2+-doped NaYF4:Yb/Er upconversion nanoparticles (NaYF4:Yb,Er/Mn UCNPs) was employed in electrogenerated chemiluminescence (ECL) for the sensitive detection of bisphenol A (BPA). The ECL aptasensor was assembled by immobilizing the thiolated aptamers of BPA covalently on a gold nanoparticle (AuNPs)-modified electrode and pairing with complementary DNA labeled with NaYF4:Yb,Er/Mn UCNPs. The ECL aptasensor can not only rapidly and accurately detect BPA concentrations from 0.05 to 100 ng/mL with a detection limit of 0.037 ng/mL but also provides a new platform for ECL applications based on the use of upconversion nanoparticles as a promising alternative material. Graphical Abstract The NaYF4:Yb,Er/Mn UCNPs combining with the BPA aptamer serving as recognition elements create a ECL platform for the sensitive detection of bisphenol A. The change in ECL signals induced by aptamer-target interactions was measured and a significant decrease in intensity was found on interaction with BPA in the concentration range of 0.05 to 100 ng/mL.
Keywords: NaYF4:Yb,Er/Mn UCNPs; Aptamer; ECL; Bisphenol A

Hasse diagram as a green analytical metrics tool: ranking of methods for benzo[a]pyrene determination in sediments by Paulina Bigus; Stefan Tsakovski; Vasil Simeonov; Jacek Namieśnik; Marek Tobiszewski (3833-3841).
This study presents an application of the Hasse diagram technique (HDT) as the assessment tool to select the most appropriate analytical procedures according to their greenness or the best analytical performance. The dataset consists of analytical procedures for benzo[a]pyrene determination in sediment samples, which were described by 11 variables concerning their greenness and analytical performance. Two analyses with the HDT were performed—the first one with metrological variables and the second one with “green” variables as input data. Both HDT analyses ranked different analytical procedures as the most valuable, suggesting that green analytical chemistry is not in accordance with metrology when benzo[a]pyrene in sediment samples is determined. The HDT can be used as a good decision support tool to choose the proper analytical procedure concerning green analytical chemistry principles and analytical performance merits.
Keywords: Multivariate statistics; Greenness assessment; Green chemistry; Benzo[a]pyrene; Chemometrics

HS–GC/MS volatile profile of different varieties of garlic and their behavior under heating by María Molina-Calle; Feliciano Priego-Capote; María D. Luque de Castro (3843-3852).
Garlic is one of the most used seasonings in the world whose beneficial health effects, mainly ascribed to organosulfur compounds, are shared with the rest of the Allium family. The fact that many of these compounds are volatile makes the evaluation of the volatile profile of garlic interesting. For this purpose, three garlic varieties—White, Purple, and Chinese—cultivated in the South of Spain were analyzed by a method based on a headspace (HS) device coupled to a gas chromatograph and mass detector (HS–GC/MS). The main temperatures in the HS were optimized to achieve the highest concentration of volatiles. A total number of 45 volatiles were tentatively identified (among them 17 were identified for the first time in garlic); then, all were classified, also for the first time, and their relative concentration in three garlic varieties was used to evaluate differences among them and to study their profiles according to the heating time. Chinese garlic was found to be the richest variety in sulfur volatiles, while the three varieties presented a similar trend under preset heating times allowing differentiation between varieties and heating time using principal component analysis. Graphical Abstract HS-GC/MS analysis of the volatile profile of garlic
Keywords: Garlic varieties; Headspace; GC/MS; Sulfur volatiles; Flavor; Heating times

Massive production of nanomaterials poses a high risk to environmental ecology and human health. However, comprehensive understanding of nanotoxicity is still a major challenge due to the limitations of assessment methods, especially at the molecular level. We developed a new, sensitive, and robust fingerprinting surface-enhanced Raman spectroscopy (SERS) approach to interrogate both dose- and time-dependent phenotypic bacterial responses to zinc oxide nanoparticles (ZnO NPs). SERS enhancement was provided by biocompatible Au NPs. Additionally, a novel vacuum filtration-based strategy was adopted to fabricate bacterial samples with highly uniform SERS signals, ensuring the acquisition of robust and independent spectral changes from ZnO NPs-impacted bacteria without undesirable spectral variations. Combined with multivariate analysis, clear and informative spectral alteration profiles were obtained. Much greater alterations were found in low-dose ranges than high-dose ranges, indicating a reduction in the bioavailability of ZnO NPs with doses. Time-resolved bacterial responses provided important information on toxic dynamics, i.e., rapid action of ZnO NPs within 0.5 h was identified, and ZnO NPs at low doses and long exposure time exerted similar effects to high doses, indicating the concerns associated with low-dose exposure. Further analysis of biochemical changes revealed metabolic activity decrease over both incubation time and doses. Meanwhile, a short-term protection strategy of bacteria by producing lipid-containing outer membrane vesicles to mitigate the cell of toxic NPs was suggested. Finally, Zn2+ ions released from NPs were demonstrated to be irrelevant to bacterial responses on both dose and time scales. The new SERS methodology can potentially profile a large variety of toxic NPs and advance our understanding of nanotoxicity. Graphical Abstract A highly uniform SERS signal of bacteria negating undesired spectral variation via a novel vacuum filtration-based strategy, combined with multivariate PCA-LDA analysis, was utilized to interrogate both dose- and time-dependent antibacterial effect of zinc oxide nanoparticles, and can be extended to a variety of other toxic nanoparticles.
Keywords: Surface-enhanced Raman spectroscopy; Antibacterial effect; ZnO nanoparticles; Dose-dependent; Time-dependent; Nanotoxicity

Depletion of internal peptides by site-selective blocking, phosphate labeling, and TiO2 adsorption for in-depth analysis of C-terminome by Lingfan Chen; Yichu Shan; Yejing Weng; Huiming Yuan; Shen Zhang; Runlong Fan; Zhigang Sui; Xiaodan Zhang; Lihua Zhang; Yukui Zhang (3867-3874).
The analysis of protein C-termini is of great importance, because it not only provides valuable information about protein function, but also facilitates the elucidation of proteolytic processing. However, even with the recent methods for the global profiling of protein C-termini, the identification of C-termini is still far behind that of N-termini due to the lack of basic residue and low reactive carboxyl group. Therefore, an unbiased and complementary method for C-termini profiling is imperative. In this work, we developed a negative enrichment strategy to achieve the in-depth analysis of C-terminome. Proteins were firstly amidated to block carboxyl groups, followed by lysyl endoproteinase (LysC) digestion to generate C-terminal peptides with α-amines and internal peptides bearing both α- and ε-amines. After the α-amines were blocked by site-selective dimethylation or succinylation, the remaining ε-amines on internal peptides were labeled with phosphate groups. Finally, internal peptides were depleted by TiO2, leaving exclusively the fraction of C-terminal peptides for LC-MS/MS analysis. With Escherichia coli (E. coli) digests as the sample, the efficiency of amidation, dimethylation/succinylation, phosphate labeling and TiO2 depletion was proved high. With the combination of dimethyl and succinic blocking strategy, our method enabled the identification of 477 unique C-terminal peptides in E. coli. In comparison with the C-terminal amine-based isotope labeling of substrates (C-TAILS) method, 83 C-termini were identified by both methods, whereas 369 C-termini were unique to C-TAILS and 394 to our dataset. The method proposed is therefore efficient and possibly promotes the comprehensive profiling of C-termini. Graphical Abstract Negative isolation of C-terminal peptides with combination of site-selective blocking, phosphate labeling, and TiO2 adsorption
Keywords: C-termini; Dimethylation; Succinylation; TiO2 particle; Proteolysis

Quantification of protein secondary structure by 13C solid-state NMR by Fabiana Diuk Andrade; Lucimara Aparecida Forato; Rubens Bernardes Filho; Luiz Alberto Colnago (3875-3879).
High-resolution 13C solid-state NMR stands out as one of the most promising techniques to solve the structure of insoluble proteins featuring biological and technological importance. The simplest nuclear magnetic resonance (NMR) spectroscopy method to quantify the secondary structure of proteins uses the areas of carbonyl and alpha carbon peaks. The quantification obtained by fitting procedures depends on the assignment of the peaks to the structure, type of line shape, number of peaks to be used, and other parameters that are set by the operator. In this paper, we demonstrate that the analysis of 13C NMR spectra by a pattern recognition method—based on the singular value decomposition (SVD) regression, which does not depend on the operator—shows higher correlation coefficients for α-helix and β-sheet (0.96 and 0.91, respectively) than Fourier transform infrared spectroscopy (FTIR) method. Therefore, the use of 13C solid-state NMR spectra and SVD is a simple and reliable method for quantifying the secondary structures of insoluble proteins in solid-state.
Keywords: 13C solid-state NMR; Protein secondary structure; Insoluble protein; Singular value decomposition

An intelligentized strategy for endogenous small molecules characterization and quality evaluation of earthworm from two geographic origins by ultra-high performance HILIC/QTOF MSE and Progenesis QI by Jingxian Zhang; Wenzhi Yang; Shangrong Li; Shuai Yao; Peng Qi; Zhou Yang; Zijin Feng; Jinjun Hou; Luying Cai; Min Yang; Wanying Wu; De-an Guo (3881-3890).
Animal-derived medicines have been a vital component for traditional Chinese medicine. However, their quality control remains challenging due to the large polarity of the contained endogenous small molecules (ESMs) that are difficult to separate by reversed-phase HPLC. Herein, an intelligentized strategy by ultra-high performance hydrophilic interaction chromatography/quadrupole time-of-flight mass spectrometry (HILIC/QTOF-MSE) is presented, and used for the ESMs characterization and differentiation of two geographic origins of earthworm (Guang Di-long, GD; Hu Di-long, HD) as a case study. Chromatographic separation was performed on a BEH Amide column (2.1 × 100 mm, 1.7 μm). The MSE data in both negative and positive ion modes were acquired to record the high-accuracy MS and MS/MS data of all precursor ions. Automatic data processing was enabled by use of Progenesis QI software. As a consequence, 926 metabolites among 4705 features and 761 among 3418 features were characterized in the negative and positive modes, respectively, by searching the human metabolome database (HMDB). To reduce the false positive identifications, structural confirmation was conducted by comparison with the reference standards (tR and MS, MS/MS data) or matching with theoretical data or commercial library. Principal component analysis (PCA) of the GD and HD samples showed distinct classifications. Further orthogonal partial least squares discriminant analysis (OPLS-DA) and variable importance in projection (VIP) plot revealed the potential discriminatory markers between GD and HD. The present study provides a powerful and practical strategy that facilitates the primary metabolites characterization and quality evaluation of animal-derived medicines more efficiently. Graphical Abstract A general flowchart illustrating the application of ultra-high performance HILIC/QTOFMSE coupled with data processing by Progenesis QI to characterization of the endogenous small molecules and discriminatory analysis of animal-derived traditional medicine: earthworm as a case study
Keywords: Animal-derived medicines; Earthworm; Endogenous small molecule; HILIC/QTOF MSE ; Progenesis QI

In vitro and in vivo stability of oseltamivir within a bioequivalence trial by Alexander Grigoriev; Irina Borisova; Irina Yaroshenko; Alla Sidorova (3891-3897).
A simple, precise, and rapid method to simultaneously determine the levels of oseltamivir (OS) and oseltamivir carboxylate (OSC) in human plasma was developed. Additionally, the stability of both substances in plasma was investigated under different conditions. The method involved protein precipitation (0.01 % HCl in acetonitrile), and then the supernatant was injected into the high-performance liquid chromatography (HPLC)-MS/MS. The chromatographic separation was achieved on a YMC-Triart C18 (100 × 2.0 mm, 5 μm) column using acetonitrile/water (30:70, v/v) containing 0.1 % formic acid as the mobile phase. Sample volume was 5 μl. The linearity of the method was established in the concentration range of 0.5–100 ng/mL for OS and 1.0–1000 ng/mL for OSC. The intra-day precision and accuracy for oseltamivir were 1.5–8.9 and 94.4–101.0 %, respectively. For oseltamivir carboxylate, the intra-day precision and accuracy were 3.2–12.7 and 92.8–108.8 %, respectively, whereas the inter-day precision and accuracy were 5.5–11.5 and 94.6–104.0 % for oseltamivir and 4.7–11.5 and 99.9–103.9 % for oseltamivir carboxylate, respectively. The application of this method was demonstrated by a bioequivalence study in 28 healthy humans with 75 mg oseltamivir phosphate capsules (Tamiflu®). Sodium fluoride (2.4 mg/mL) with potassium oxalate (3 mg/mL) was used as anticoagulant within sampling of trial. The assay reproducibility was established by reanalysis of 80 incurred samples.
Keywords: Oseltamivir; Oseltamivir carboxylate; Stability; HPLC-MS/MS; Bioequivalence study; Pharmacokinetics

This work describes the first report about the simultaneous determination of levodopa (l-DOPA) with folic acid (FA) and uric acid (UA) based on electrocatalytic oxidation of l-DOPA with peroxidase properties of hemoglobin (Hb) in the presence of H2O2 as Hb activator. Bovine Hb was electrostatically immobilized on WO3 nanoparticles (WO3NPs) in pH between Hb and WO3NP isoelectric points, and subsequently, a carbon paste electrode (CPE) was modified with the obtained WO3NPs-Hb and multiwalled carbon nanotubes (MWCNTs). The resulting biosensor supplied a sensitive and suitably stable biosensor for the simultaneous determination of l-DOPA, UA, and FA. The obtained linear range and detection limit for l-DOPA, UA, and FA were completely acceptable, and the biosensor response time for these molecules was relatively short so that it reaches about 95 % of its maximum response in less than 10 s. The applicability of the current biosensor was confirmed with the determination of l-DOPA in the presence of fixed amounts of FA and UA in some real samples by the standard addition method.
Keywords: Biosensor; Hemoglobin; Simultaneous determination; Levodopa; Folic acid; Uric acid

Liquid chromatography-mass spectrometry as a general approach for investigating covalent binding of drugs to DNA by Maria Raja; Joan Albertí; Javier Saurina; Sonia Sentellas (3911-3922).
This paper aims at developing a general strategy to study the detection of adducts of drugs with DNA. In particular, ethacrynic acid has been chosen as a model reactive drug that could be able to bind covalently to DNA bases. Such interactions were detected by ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS). Principal component analysis (PCA) was applied as an unsupervised method to try to find the potential candidate adduct from MS features. The occurrence of adducts was investigated preliminarily using deoxynucleosides of the guanine, cytosine, adenine, and thymine separately as a way to optimize both separation and detection conditions. Interpretations of MS and MS/MS spectra provided tentative structures of the compounds formed. Conclusions extracted from such simple nucleoside models were further extended to the analysis of DNA adducts. For such a purpose, DNA was incubated in the presence of ethacrynic acid under appropriate experimental conditions and its further enzymatic hydrolysis released the corresponding nucleosides. UHPLC-MS analysis of the resulting test samples under the SRM detection mode confirmed the presence of ethacrynic acid derivatives of nucleosides occurring at very low concentration levels, thus proving the overall performance of the method. Graphical Abstract General approach for investigating drug-DNA adduct formation
Keywords: DNA adduct; Principal component analysis; High resolution mass spectrometry; UHPLC; Deoxynucleoside adduct