Identifications of novel host cell factors that interact with the receptor-binding domain of the SARS-CoV-2 spike protein.

SARS-CoV-2 entry into host cells is facilitated by the interaction between the receptor-binding domain of its spike protein (CoV2-RBD) and host cell receptor, ACE2, promoting viral membrane fusion. The virus also uses endocytic pathways for entry, but the mediating host factors remain largely unknown. It is also unknown whether mutations in the RBD of SARS-CoV-2 variants promote interactions with additional host factors to promote viral entry. Here, we used the GST pull-down approach to identify novel surface-located host factors that bind to CoV2-RBD. One of these factors, SH3BP4, regulates internalization of CoV2-RBD in an ACE2-independent but integrin- and clathrin-dependent manner and mediates SARS-CoV-2 pseudovirus entry, suggesting that SH3BP4 promotes viral entry via the endocytic route. Many of the identified factors, including SH3BP4, ADAM9, and TMEM2, show stronger affinity to CoV2-RBD than to RBD of the less infective SARS-CoV, suggesting SARS-CoV-2-specific utilization. We also found factors preferentially binding to the RBD of the SARS-CoV-2 Delta variant, potentially enhancing its entry. These data identify the repertoire of host cell surface factors that function in the events leading to the entry of SARS-CoV-2.

Discovery of a novel class of rosmarinic acid derivatives as antibacterial agents: Synthesis, structure-activity relationship and mechanism of action.

Twenty-seven rosmarinic acid derivatives were synthesized, among which compound RA-N8 exhibited the most potent antibacterial ability. The minimum inhibition concentration of RA-N8 against both S. aureus (ATCC 29213) and MRSA (ATCC BAA41 and ATCC 43300) was found to be 6 µg/mL, and RA-N8 killed E. coli (ATCC 25922) at 3 µg/mL in the presence of polymyxin B nonapeptide (PMBN) which increased the permeability of E. coli. RA-N8 exhibited a weak hemolytic effect at the minimum inhibitory concentration. SYTOX Green assay, SEM, and LIVE/DEAD fluorescence staining assay proved that the mode of action of RA-N8 is targeting bacterial cell membranes. Furthermore, no resistance in wildtype S. aureus developed after incubation with RA-N8 for 20 passages. Cytotoxicity studies further demonstrated that RA-N8 is non-toxic to the human normal cell line (HFF1). RA-N8 also exerted potent inhibitory ability against biofilm formation of S. aureus and even collapsed the shaped biofilm.

The structural dynamics of full-length divisome transmembrane proteins FtsQ, FtsB, and FtsL in FtsQBL complex formation.

FtsQBL is a transmembrane protein complex in the divisome of Escherichia coli that plays a critical role in regulating cell division. Although extensive efforts have been made to investigate the interactions between the three involved proteins, FtsQ, FtsB, and FtsL, the detailed interaction mechanism is still poorly understood. In this study, we used hydrogen-deuterium exchange mass spectrometry to investigate these full-length proteins and their complexes. We also dissected the structural dynamic changes and the related binding interfaces within the complexes. Our data revealed that FtsB and FtsL interact at both the periplasmic and transmembrane regions to form a stable complex. Furthermore, the periplasmic region of FtsB underwent significant conformational changes. With the help of computational modeling, our results suggest that FtsBL complexation may bring the respective constriction control domains (CCDs) in close proximity. We show that when FtsBL adopts a coiled-coil structure, the CCDs are fixed at a vertical position relative to the membrane surface; thus, this conformational change may be essential for FtsBL's interaction with other divisome proteins. In the FtsQBL complex, intriguingly, we show only FtsB interacts with FtsQ at its C-terminal region, which stiffens a large area of the ß-domain of FtsQ. Consistent with this, we found the connection between the α- and ß-domains in FtsQ is also strengthened in the complex. Overall, the present study provides important experimental evidence detailing the local interactions between the full-length FtsB, FtsL, and FtsQ protein, as well as valuable insights into the roles of FtsQBL complexation in regulating divisome activity.

Interdomain flexibility and interfacial integrity of ß-lactamase inhibitory protein (BLIP) modulate its binding to class A ß-lactamases.

ß-Lactamase inhibitory protein (BLIP) consists of a tandem repeat of αß domains conjugated by an interdomain loop and can effectively bind and inactivate class A ß-lactamases, which are responsible for resistance of bacteria to ß-lactam antibiotics. The varied ability of BLIP to bind different ß-lactamases and the structural determinants for significant enhancement of BLIP variants with a point mutation are poorly understood. Here, we investigated the conformational dynamics of BLIP upon binding to three clinically prevalent class A ß-lactamases (TEM1, SHV1, and PC1) with dissociation constants between subnanomolar and micromolar. Hydrogen deuterium exchange mass spectrometry revealed that the flexibility of the interdomain region was significantly suppressed upon strong binding to TEM1, but was not significantly changed upon weak binding to SHV1 or PC1. E73M and K74G mutations in the interdomain region improved binding affinity toward SHV1 and PC1, respectively, showing significantly increased flexibility of the interdomain region compared to the wild-type and favorable conformational changes upon binding. In contrast, more rigidity of the interfacial loop 135-145 was observed in these BLIP mutants in both free and bound states. Consistently, molecular dynamics simulations of BLIP exhibited drastic changes in the flexibility of the loop 135-145 in all complexes. Our results indicated for the first time that higher flexibility of the interdomain linker, as well as more rigidity of the interfacial loop 135-145, could be desirable determinants for enhancing inhibition of BLIP to class A ß-lactamases. Together, these findings provide unique insights into the design of enhanced inhibitors.

Advances in rapid detection of SARS-CoV-2 by mass spectrometry.

COVID-19 has already been lasting for more than two years and it has been severely affecting the whole world. Still, detection of SARS-CoV-2 remains the frontline approach to combat the pandemic, and the reverse transcription polymerase chain reaction (RT-PCR)-based method is the well recognized detection method for the enormous analytical demands. However, the RT-PCR method typically takes a relatively long time, and can produce false positive and false negative results. Mass spectrometry (MS) is a very commonly used technique with extraordinary sensitivity, specificity and speed, and can produce qualitative and quantitative information of various analytes, which cannot be achieved by RT-PCR. Since the pandemic outbreak, various mass spectrometric approaches have been developed for rapid detection of SARS-CoV-2, including the LC-MS/MS approaches that could allow analysis of several hundred clinical samples per day with one MS system, MALDI-MS approaches that could directly analyze clinical samples for the detection, and efforts for the on-site detection with portable devices. In this review, these mass spectrometric approaches were summarized, and their pros and cons as well as further development were also discussed.

Structure of mouse cytosolic sulfotransferase SULT2A8 provides insight into sulfonation of 7α-hydroxyl bile acids.

Cytosolic sulfotransferases (SULTs) catalyze the transfer of a sulfonate group from the cofactor 3'-phosphoadenosine 5'-phosphosulfate to a hydroxyl (OH) containing substrate and play a critical role in the homeostasis of endogenous compounds, including hormones, neurotransmitters, and bile acids. In human, SULT2A1 sulfonates the 3-OH of bile acids; however, bile acid metabolism in mouse is dependent on a 7α-OH sulfonating SULT2A8 via unknown molecular mechanisms. In this study, the crystal structure of SULT2A8 in complex with adenosine 3',5'-diphosphate and cholic acid was resolved at a resolution of 2.5 Å. Structural comparison with human SULT2A1 reveals different conformations of substrate binding loops. In addition, SULT2A8 possesses a unique substrate binding mode that positions the target 7α-OH of the bile acid close to the catalytic site. Furthermore, mapping of the critical residues by mutagenesis and enzyme activity assays further highlighted the importance of Lys44 and His48 for enzyme catalysis and Glu237 in loop 3 on substrate binding and stabilization. In addition, limited proteolysis and thermal shift assays suggested that the cofactor and substrates have protective roles in stabilizing SULT2A8 protein. Together, the findings unveil the structural basis of bile acid sulfonation targeting 7α-OH and shed light on the functional diversity of bile acid metabolism across species.

Conformational Dynamics of the Helix 10 Region as an Allosteric Site in Class A ß-Lactamase Inhibitory Binding.

ß-Lactamase inhibitory protein (BLIP) can effectively inactivate class A ß-lactamases, but with very different degrees of potency. Understanding the different roles of BLIP in class A ß-lactamases inhibition can provide insights for inhibitor design. However, this problem was poorly solved on the basis of the static structures obtained by X-ray crystallography. In this work, ion mobility mass spectrometry, hydrogen-deuterium exchange mass spectrometry, and molecular dynamics simulation revealed the conformational dynamics of three class A ß-lactamases with varying inhibition efficiencies by BLIP. A more extended conformation of PC1 was shown compared to those of TEM1 and SHV1. Localized dynamics differed in several important loop regions, that is, the protruding loop, H10 loop, Ω loop, and SDN loop. Upon binding with BLIP, these loops cooperatively rearranged to enhance the binding interface and to inactivate the catalytic sites. In particular, unfavorable changes in conformational dynamics were found in the protruding loop of SHV1 and PC1, showing less effective binding. Intriguingly, the single mutation on BLIP could compensate for the unfavored changes in this region, and thus exhibit enhanced inhibition toward SHV1 and PC1. Additionally, the H10 region was revealed as an important allosteric site that could modulate the inhibition of class A ß-lactamases. It was suggested that the rigid protruding loop and flexible H10 region might be determinants for the effective inhibition of TEM1. Our findings provided unique and explicit insights into the conformational dynamics of ß-lactamases and their bindings with BLIP. This work can be extended to other ß-lactamases of interest and inspire the design of novel inhibitors.

Hydrophobic substituents on isatin derivatives enhance their inhibition against bacterial peptidoglycan glycosyltransferase activity.

Moenomycin A, the well-known natural product inhibitor of peptidoglycan glycosyltransferase (PGT), is a large amphiphilic molecule of molecular mass of 1583 g/mol and its bioavailablity as a drug is relatively poor. In searching for small-molecule ligands with high inhibition ability targeting the enzyme, we found that the addition of hydrophobic groups to an isatin-based inhibitor of bacterial PGT significantly improves its inhibition against the enzyme, as well as its antibacterial activity. The improvement in enzymatic inhibition can be attributed to a better binding of the small molecule inhibitor to the hydrophobic region of the membrane-bound bacterial cell wall synthesis enzyme and the plasma membrane. In the present study, a total of 20 new amphiphilic compounds were systematically designed and the relationship between molecular hydrophobicity and the antibacterial activity by targeting at PGT was demonstrated. The in vitro lipid II transglycosylation inhibitory effects (IC50) against E. coli PBP1b and MICs of the compounds were investigated. Optimized results including MIC values of 6 µg/mL for MSSA, MRSA, B. subtilis and 12 µg/mL for E. coli were obtained with an isatin derivative 5m which has a molecular mass of 335 g/mol.

A bioengineered arginine-depleting enzyme as a long-lasting therapeutic agent against cancer.

L-Arginine (L-Arg) depletion has attracted great attention in cancer therapy. Although two types of arginine-depleting enzymes, arginine deiminase (ADI) and human arginase I, are undergoing clinical trials, random site of PEGylation, low efficacy of heavy metal as co-factor, and immunogenicity limit the performance of these drugs and cause difficulty in a homogeneous production. Here we screened ten catalytic metal ions and have successfully produced a site-specific mono-PEGylated human arginase I mutant by conjugating the Cys45 residue to PEG-maleimide to minimize the decrease in activity and produce a homogeneous product. The catalytic efficiency trend of metal ion-enriched human arginase I mutant (HAI) was Co2+ > Ni2+ ≫ Mn2+. The overall kcat/KM values of Co-HAI and Ni-HAI were higher than Mn-HAI by ~ 8.7- and ~ 5.2-folds, respectively. Moreover, the results of enzyme kinetics and circular dichroism spectrometry demonstrated that the 20 or 40 kDa linear and branched PEG attached on the HAI surface did not affect the enzyme activity and the protein secondary structures. In vitro studies showed that both Co-HAI-PEG20L and Ni-HAI-PEG20L inhibited the growth of eight types of cancer cell lines. The pharmacodynamic study in mice demonstrated that the i.p. administration of Co-HAI-PEG20L at 13 mg/kg and Ni-HAI-PEG20L at 15 mg/kg was able to maintain a L-Arg level below its detection limit for over 120 h after one injection. The body weights of mice could return to normal levels within 5 days after injection, showing that the doses were well-tolerated. Therefore, both the Ni-HAI-PEG20L and Co-HAI-PEG20L are promising candidates for cancer therapy. KEY POINTS: • Mono-PEGylation applied on human arginase I mutant (HAI) successfully. • The catalytic efficiency of Co- and Ni-enriched HAI was higher than the wild type. • At least eight types of cancer cell lines were inhibited by Co- and Ni-HAI-PEG20L. • Co- and Ni-HAI-PEG20L were able to achieve weekly depletion of L-Arg. Graphical abstract.

Mono-PEGylation of a Thermostable Arginine-Depleting Enzyme for the Treatment of Lung Cancer.

L-arginine (L-Arg) depletion induced by randomly PEGylated arginine deiminase (ADI-PEG20) can treat arginosuccinate synthase (ASS)-negative cancers, and ADI-PEG20 is undergoing phase III clinical trials. Unfortunately, ASS-positive cancers are resistant to ADI-PEG20. Moreover, the yield of ADI production is low because of the formation of inclusion bodies. Here, we report a thermostable arginine-depleting enzyme, Bacillus caldovelox arginase mutant (BCA-M: Ser161->Cys161). An abundant amount of BCA-M was easily obtained via high cell-density fermentation and heat treatment purification. Subsequently, we prepared BCA-M-PEG20, by conjugating a single 20 kDa PEG monomer onto the Cys161 residue via thio-chemistry. Unlike ADI-PEG20, BCA-M-PEG20 significantly inhibited ASS-positive lung cancer cell growth. Pharmacodynamic studies showed that a single intraperitoneal injection (i.p). administration of 250 U/mouse of BCA-M-PEG20 induced low L-Arg level over 168 h. The mono-PEGylation of BCA-M prolonged its elimination half-life from 6.4 to 91.4 h (a 14-fold increase). In an A549 lung cancer xenograft model, a weekly administration of 250 U/mouse of BCA-M-PEG20 suppressed tumor growth significantly. We also observed that BCA-M-PEG20 did not cause any significant safety issue in mouse models. Overall, BCA-M-PEG20 showed excellent results in drug production, potency, and stability. Thereby, it has great potential to become a promising candidate for lung cancer therapy.

Simple Fabrication of Solid-Phase Microextraction with Surface-Coated Aluminum Foil for Enhanced Detection of Analytes in Biological and Clinical Samples by Mass Spectrometry.

Rapid detection of analytes in biological and clinical samples is highly desirable, and significant progress has been made with direct mass spectrometric (MS) analysis. Rapid and sensitive detection, however, remains a major challenge in direct analysis of raw samples. In this study, we described a simple, rapid, and efficient method for enhanced detection of analytes in complex samples, using surface-coated aluminum (Al) foil that was simply made with conductive resin for physical adhesion of functional particles. The surface-coated Al foils were used as a solid-phase microextraction (SPME) tip for rapid sampling of target analytes from raw samples and then applied as an electrospray ionization (ESI) tip to couple MS for sensitive detection. Our results show that surface-coated Al foil is highly effective for enhanced detection of analytes in complex samples with excellent analytical performances, including sensitivity, reproducibility, and linear ranges. Overall, this development enabled an extremely simplified protocol to integrate SPME and ESI that is expected to have a significant impact on rapid screening of raw samples.

Protein dynamics revealed by hydrogen/deuterium exchange mass spectrometry: Correlation between experiments and simulation.

Hydrogen deuterium exchange mass spectrometry (HDX-MS) is a powerful technique for studying protein dynamics, which is an important factor governing protein functions. However, the process of hydrogen/deuterium exchange (HDX) of proteins is highly complex and the underlying mechanism has not yet been fully elucidated. Meanwhile, molecular dynamics (MD) simulation is a computational technique that can be used to elucidate HDX behaviour on proteins and facilitate interpretation of HDX-MS data. This article aims to summarize the current understandings on the mechanism of HDX and its correlation with MD simulation, to discuss the recent developments in the techniques of HDX-MS and MD simulation and to extend the perspectives of these two techniques in protein dynamics study.

Surface-Modified Wooden-Tip Electrospray Ionization Mass Spectrometry for Enhanced Detection of Analytes in Complex Samples.

Replacement of capillary with solid substrates for sample loading and ionization has created many new possibilities for electrospray ionization mass spectrometry (ESI-MS). Surface modification is an attractive strategy to enhance the analytical capability of solid-substrate ESI-MS and allow understanding the relationship between surface activity of solid substrates and analytical properties. In this study, we performed surface modification of wooden tips with hydrophobic (-C18), basic (-NH2), and acidic (-SO3H) functional groups and applied various sampling methods, i.e., extractive sampling and direct loading, to comprehensively investigate the analytical properties of solid-substrate ESI-MS. Our results showed that, for the direct loading method, analytes with weak interactions with solid-substrate surface could be readily sprayed out for detection. While for the extractive sampling method, analytes strongly retained on solid-substrate surface could be selectively enriched and detected, and a washing step after sample loading could effectively remove unbound components for reducing interference. Overall, the insights on the effects of surface-analyte interactions on the analytical features obtained in this study could aid the development of surface-modified strategies for enhancing the analytical capability of solid-substrate ESI-MS.

The analysis of alpha-1-antitrypsin glycosylation with direct LC-MS/MS.

A liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based methodology has been developed to differentiate core- and antennary-fucosylated glycosylation of glycopeptides. Both the glycosylation sites (heterogeneity) and multiple possible glycan occupancy at each site (microheterogeneity) can be resolved via intact glycopeptide analysis. The serum glycoprotein alpha-1-antitrypsin (A1AT) which contains both core- and antennary-fucosylated glycosites was used in this study. Sialidase was used to remove the sialic acids in order to simplify the glycosylation microheterogeneity and to enhance the MS signal of glycopeptides with similar glycan structures. ß1-3,4 galactosidase was used to differentiate core- and antennary-fucosylation. In-source dissociation was found to severely affect the identification and quantification of glycopeptides with low abundance glycan modification. The settings of the mass spectrometer were therefore optimized to minimize the in-source dissociation. A three-step mass spectrometry fragmentation strategy was used for glycopeptide identification, facilitated by pGlyco software annotation and manual checking. The collision energy used for initial glycopeptide fragmentation was found to be crucial for improved detection of oxonium ions and better selection of Y1 ion (peptide+GlcNAc). Structural assignments revealed that all three glycosylation sites of A1AT glycopeptides contain complex N-glycan structures: site Asn70 contains biantennary glycans without fucosylation; site Asn107 contains bi-, tri- and tetra-antennary glycans with both core- and antennary-fucosylation; site Asn271 contains bi- and tri-antennary glycans with both core- and antennary-fucosylation. The relative intensity of core- and antennary-fucosylation on Asn107 was similar to that of the A1AT protein indicating that the glycosylation level of Asn107 is much larger than the other two sites.

Targeting the Thioredoxin Reductase-Thioredoxin System from Staphylococcus aureus by Silver Ions.

The thioredoxin system, which is composed of NADPH, thioredoxin reductase (TrxR), and thioredoxin (Trx), is one of the major disulfide reductase systems used by bacteria against oxidative stress. In particular, this reductase system is crucial for the survival of the pathogenic bacterium Staphylococcus aureus, which lacks a natural glutathione/glutaredoxin (Grx) system. Although silver ions and silver-containing materials have been used as antibacterial agents for centuries, the antibacterial mechanism of silver is not well-understood. Herein, we demonstrate that silver ions bind to the active sites of S. aureus TrxR and Trx with dissociation constants of 1.4 ± 0.1 µM and 15.0 ± 5.0 µM and stoichiometries of 1 and 2 Ag+ ions per protein, respectively. Importantly, silver ion binding leads to oligomerization and functional disruption of TrxR as well as Trx. Silver also depleted intracellular thiol levels in S. aureus, disrupting bacterial thiol-redox homeostasis. Our study provides new insights into the antibacterial mechanism of silver ions. Moreover, the Trx and TrxR system might serve as a feasible target for the design of antibacterial drugs.

Global detection and semi-quantification of Fritillaria alkaloids in Fritillariae Ussuriensis Bulbus by a non-targeted multiple reaction monitoring approach.

Methods based on triple quadrupole tandem mass spectrometry have been widely used and reported as highly selective and sensitive methods for quantifying substances of herbal medicines. However, most of them were limited to targeted components, due to the difficulties to optimize the multiple reaction monitoring transitions without authentic standards. This study proposed a novel strategy for non-targeted optimization of multiple reaction monitoring method based on the diagnostic ion guided family classifications, tandem mass spectrometry database establishment, and transitions and collision energy screening. Applying this strategy, 59 Fritillaria alkaloids in Fritillariae Ussuriensis Bulbus have been classified, and 51 of these Fritillaria alkaloids were successfully detected by the optimal multiple reaction monitoring method. For semi-quantification, the easy-to-obtain Fritillaria alkaloids of each type, such as verticinone for cevanine type and peimisine for jervine type, were used as the reference standards to calibrate the other Fritillaria alkaloids in the same type. The method was demonstrated a good linearity (R(2) > 0.998) with satisfactory accuracy and precision, and the lower limits of quantification of verticinone and peimisine were estimated to be 0.076 and 0.216 pg, respectively. In addition, the results suggested that the proposed strategy might obtained high quality metabolomics data in discrimination of Fritillaria unibracteata and Fritillaria ussuriensis.

A general strategy for site-directed enzyme immobilization by using NiO nanoparticle decorated mesoporous silica.

Mesoporous materials have recently gained much attention owing to their large surface area, narrow pore size distribution, and superior pore structure. These materials have been demonstrated as excellent solid supports for immobilization of a variety of proteins and enzymes for their potential applications as biocatalysts in the chemical and pharmaceutical industries. However, the lack of efficient and reproducible methods for immobilization has limited the activity and recyclability of these biocatalysts. Furthermore, the biocatalysts are usually not robust owing to their rapid denaturation in bulk solvents. To solve these problems, we designed a novel hybrid material system, mesoporous silica immobilized with NiO nanoparticles (SBA-NiO), wherein enzyme immobilization is directed to specific sites on the pore surface of the material. This yielded the biocatalytic species with higher activity than free enzyme in solution. These biocatalytic species are recyclable with minimal loss of activity after several cycles, demonstrating an advantage over free enzymes.

Metabolomics studies in common multifactorial eye disorders: a review of biomarker discovery for age-related macular degeneration, glaucoma, diabetic retinopathy and myopia.

Introduction: Multifactorial Eye disorders are a significant public health concern and have a huge impact on quality of life. The pathophysiological mechanisms underlying these eye disorders were not completely understood since functional and low-throughput biological tests were used. By identifying biomarkers linked to eye disorders, metabolomics enables early identification, tracking of the course of the disease, and personalized treatment. Methods: The electronic databases of PubMed, Scopus, PsycINFO, and Web of Science were searched for research related to Age-Related macular degeneration (AMD), glaucoma, myopia, and diabetic retinopathy (DR). The search was conducted in August 2023. The number of cases and controls, the study's design, the analytical methods used, and the results of the metabolomics analysis were all extracted. Using the QUADOMICS tool, the quality of the studies included was evaluated, and metabolic pathways were examined for distinct metabolic profiles. We used MetaboAnalyst 5.0 to undertake pathway analysis of differential metabolites. Results: Metabolomics studies included in this review consisted of 36 human studies (5 Age-related macular degeneration, 10 Glaucoma, 13 Diabetic retinopathy, and 8 Myopia). The most networked metabolites in AMD include glycine and adenosine monophosphate, while methionine, lysine, alanine, glyoxylic acid, and cysteine were identified in glaucoma. Furthermore, in myopia, glycerol, glutamic acid, pyruvic acid, glycine, cysteine, and oxoglutaric acid constituted significant metabolites, while glycerol, glutamic acid, lysine, citric acid, alanine, and serotonin are highly networked metabolites in cases of diabetic retinopathy. The common top metabolic pathways significantly enriched and associated with AMD, glaucoma, DR, and myopia were arginine and proline metabolism, methionine metabolism, glycine and serine metabolism, urea cycle metabolism, and purine metabolism. Conclusion: This review recapitulates potential metabolic biomarkers, networks and pathways in AMD, glaucoma, DR, and myopia, providing new clues to elucidate disease mechanisms and therapeutic targets. The emergence of advanced metabolomics techniques has significantly enhanced the capability of metabolic profiling and provides novel perspectives on the metabolism and underlying pathogenesis of these multifactorial eye conditions. The advancement of metabolomics is anticipated to foster a deeper comprehension of disease etiology, facilitate the identification of novel therapeutic targets, and usher in an era of personalized medicine in eye research.

Fluorescently Modified NDM-1: A Versatile Drug Sensor for Rapid In Vitro ß-Lactam Antibiotic and Inhibitor Screening.

We successfully developed a fluorescent drug sensor from clinically relevant New Delhi metallo-ß-lactamase-1 (NDM-1). The F70 residue was chosen to be replaced with a cysteine for conjugation with thiol-reactive fluorescein-5-maleimide to form fluorescent F70Cf, where "f" refers to fluorescein-5-maleimide. Our proteolytic studies of unlabeled F70C and labeled F70Cf monitored by electrospray ionization-mass spectrometry (ESI-MS) revealed that fluorescein-5-maleimide was specifically linked to C70 in 1:1 mole ratio (F70C:fluorophore). Our drug sensor (F70Cf) can detect the ß-lactam antibiotics cefotaxime and cephalothin by giving stronger fluorescence in the initial binding phase and then declining fluorescence signals as a result of the hydrolysis of the antibiotics into acid products. F70Cf can also detect non-ß-lactam inhibitors (e.g., l-captopril, d-captopril, dl-thiorphan, and thanatin). In all cases, F70Cf exhibits stronger fluorescence due to inhibitor binding and subsequently sustained fluorescence signals in a later stage. Native ESI-MS results show that F70Cf can bind to all four inhibitors. Moreover, our drug sensor is compatible with a high-throughput microplate reader and has the capability to perform in vitro drug screening.

Rapid detection and quantitation of ketamine and norketamine in urine and oral fluid by wooden-tip electrospray ionization mass spectrometry.

Drug analysis is an indispensable task in controlling drug abuse, which is a serious problem worldwide nowadays. In this study, we report a simple and rapid approach for detection and quantitation of drugs-of-abuse in urine and oral fluid by wooden-tip electrospray ionization mass spectrometry (WT-ESI-MS). We demonstrated that ketamine, one of the most common abused drugs, and its major metabolite, norketamine, in raw urine and oral fluid could be readily detected and quantified by WT-ESI-MS with only little sample preparation and no chromatographic separation, and the analytical performances, including the linear range, accuracy, precision, LOD and LOQ, were well acceptable for analysis of real samples.