Exploration of the potential neuroprotective compounds targeting GluN1-GluN2B NMDA receptors.

The N-methyl-d-aspartic acid (NMDA) receptors belongs to the family of ionotropic glutamate receptors, which could mediate most excitatory synaptic transmission in the brain. It is interesting to know if some available drugs have regulatory effects on the NMDARs. Herein, the present study reports the discovery of drugs targeting NMDAR using virtual screening. In this study, talniflumate with the EC50 value at 61.49 nM was successfully screened. The interaction analysis of this compound was further explored through molecular dynamics simulation. It is indicated that talniflumate could form stable interactions with GluN1-GluN2B NMDA receptors. In particular, H-bond interactions with high occupancies between GluN1-GluN2B NMDA receptors and talniflumate were observed. Compared to de novo drug discovery, this approach could be an alternative choice for development of safety and efficiency NMDAR inhibitors from available drugs.Communicated by Ramaswamy H. Sarma.

Discovery of a cysteine-rich peptide with glycation modification from Achyranthes bidentata Blume.

Cysteine-rich peptides (CRPs) are stable molecules that contain multiple disulphide bonds. Various CRPs are found in plants and animals, representing potential compounds for drug development with diverse activities. Modification of CRPs, such as glycation, has attracted increased attention due to its special structural and functional properties. Hence, this study explored a CRP isolated from the Chinese herb Achyranthes bidentata Blume, which contains a glycation modification. Herein, a reverse phase high-performance liquid chromatography system with mobile phases was used to extract and purify the peptide. The eluted peptide was detected using high resolution mass spectrometry and structurally identified using high resolution mass spectrometry and nuclear magnetic resonance. The effect of the peptide on the viability of N-methyl-D-aspartic acid (NMDA)-induced HT22 cells was determined using a cell assay. Here, a new cysteine-rich glycation peptide, termed glycation-bidentatide (Gly-BTP), with three pairs of disulphide bonds and a glycation modification at the N-terminus linked to cysteine, was discovered. Cell bioactivity assay results suggested that Gly-BTP might be a potential therapeutic and provide a neuroprotective effect in NMDA-induced HT22 murine hippocampal neuronal cells. The discovery of Gly-BTP will promote the understanding of the role of CRPs in neuroprotection.

Computational exploration of natural peptides targeting ACE2.

Interaction between the SARS-COV-2 (2019 novel coronavirus) spike protein and ACE2 receptors expressed on cellular surfaces initialises viral attachment and consequent infection. Blocking this interaction shows promise for blocking or ameliorating the virus' pathological effects on the body. By contrast to work focusing on the coronavirus, which has significant potential diversity through possible accumulation of mutations during transmission, targeting the conserved ACE2 protein expressed on human cells offers an attractive alternative route to developing pharmacological prophylactics against viral invasion. In this study, we screened a virtual database of natural peptides in silico, with ACE2 as the target, and performed structural analyses of the interface region in the SARS-COV-2 RBD/ACE2 complex. These analyses have identified 15 potentially effective compounds. Analyses of ACE2/polypeptide interactions suggest that these peptides can block viral invasion of cells by stably binding in the ACE2 active site pocket. Molecular simulation results for Complestatin and Valinomycin indicate that they may share this mechanism. The discovery of this probable binding mechanism provides a frame of reference for further optimization, and design of high affinity ACE2 inhibitors that could serve as leads for production of drugs with preventive and therapeutic effects against SARS-COV-2. Communicated by Ramaswamy H. Sarma.

Plasma nontargeted peptidomics discovers potential biomarkers for major depressive disorder.

PURPOSE: There are great demands for identifying biomarkers of major depressive disorder (MDD), a common mental illness with a prevalence of approximately 6%. Finding potential biomarkers to aid MDD diagnosis is in high demand. EXPERIMENTAL DESIGN: In this study, a combination of pretreatment methods named salt-out assisted liquid-liquid extraction (SALLE) and nontargeted peptidomics based on nano-LC-Orbitrap/MS was primarily employed to discover the candidate peptide markers from the plasma of 238 subjects. RESULTS: Many peptides were enriched and identified from the plasma, 42 of which showed significant differences between MDD patients and controls by univariate statistical analysis. A binary logistic regression (BLR) model combined four peptide markers (P1, P9, P17, P29) was established, yielding an overall prediction accuracy of 91.7% and 82.2% in the discovery and validation sets, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: In conclusion, the excellent performance of the BLR model in both discovery and validation sets demonstrates the robustness of the four peptide markers panel. It is very valuable for quantification of the absolute content of four peptides and further verification.

Measurement of ultra-trace level of intact oxytocin in plasma using SALLE combined with nano-LC-MS.

Measurement of peptides such as oxytocin in plasma is a critical challenge in clinical research because of their extreme low concentrations as well as the tremendous interferencing substances co-presented in plasma. In this study, we developed an efficient salt-out assisted liquid-liquid extraction (SALLE) to treat plasma, and then analyzed the samples using nano-LC-MS to quantify intact oxytocin (OT) in human and rat plasmas. Our results showed that the use of SALLE (Isopropanol/K2HPO4 (4 M)) allows efficient removal of various disrupters, including proteins, inorganic salts, and lipids, which helps avoid the risk of blocked capillary columns and matrix effects. Moreover, instant SALLE can reduce the possible binding between OT and proteins, thus allowing high repeatability of OT extraction from the original plasma. This combination of SALLE and nano-LC-MS method provided in the end a 1 pg/m L of detection limit. Comparative analysis showed that the concentration of OT in the plasma taken from 12 volunteers ranged from 3 to 214 pg/m L, about one order less than those in the plasma of rats. Compared to the previously reported LC-MS and immunoassay methods, the combination of SALLE and nano-LC-MS permits reliable measurement of intact OT even in human plasma. Our approach may be an alternative method for quantitative determination of other ultra-trace peptides in plasma, which would help the investigators understand the role of peptides in behaviours and diseases.

Extensive characterization and differential analysis of endogenous peptides from Bombyx batryticatus using mass spectrometric approach.

Bombyx batryticatus, the dried larva of Bombyx mori L. (4th-5th instars) infected with Beauveria bassiana Vuill, is an important animal-derived medicine effective against several diseases. The metamorphosis of silkworm can result insignificant changes in the levels of proteins and polypeptides in the 4th and 5th instar larvae. Here, we performed extensive characterization of Bombyx batryticatus peptides, including polypeptides containing cysteines, using an MS-based data mining strategy. A total of 779 peptides with various PTMs (post-translational modifications) were identified through database search and de novo sequencing. Some of these peptides might have important biological activities. Besides, the differential analysis of polypeptides between the head and body of Bombyx batryticatus was performed to provide a clinical basis for rational use of the drugs derived from it. This study illustrates the abundance and sequences of endogenous Bombyx batryticatus polypeptides, and thus, provides potential candidates for the screening of active compounds for future biological research and drug discovery studies.

Rapid discrimination between red and white ginseng based on unique mass-spectrometric features.

Red ginseng (RG) and white ginseng (WG), two processed products of Panax ginseng C. A. Meyer, are in high demand due to their unique features. In this study, some of these unique features were identified and confirmed as biomarkers of RG by using ultra-high-performance liquid chromatography-mass spectrometry, data mining, support vector machine, and artificial neural network. Principal component analysis showed clear separation between the RG and WG extracts, indicating the presence of potential discriminators. In addition, 20 features that are dominant in RG were found by data mining. Samples of Panax quinquefolium (PQ) and Panax notoginseng (PN), close relatives of Panax ginseng C.A.Meyer, were investigated and it was found that 17 features which were absent in PQ and PN samples, were present in RG and WG. Five of these markers were identified as nitrogen-containing compounds that have not been previously reported. Finally, we found that RG can be identified among different ginseng medicinal herbs including RG, WG, PQ, and PN samples, by loading four feature markers corresponding to nitrogen-containing compounds into a discriminating model, based on a support vector machine or an artificial neural network. Thus, this study provides an efficient tool to identify RG during pharmacological research.