Study on the secondary structure and hydration effect of human serum albumin under acidic pH and ethanol perturbation with IR/NIR spectroscopy

Human serum albumin(HSA)is the most abundant protein in plasma and plays an essential physiological role in the human body.Ethanol precipitation is the most widely used way to obtain HSA,and pH and ethanol are crucial factors affecting the process.In this study,infrared(IR)spectroscopy and near-infrared(NIR)spectroscopy in combination with chemometrics were used to investigate the changes in the secondary structure and hydration of HSA at acidic pH(5.6-3.2)and isoelectric pH when ethanol concentration was varied from 0%to 40%as a perturbation.IR spectroscopy combined with the two-dimensional correlation spectroscopy(2DCOS)analysis for acid pH system proved that the secondary structure of HSA changed significantly when pH was around 4.5.What's more,the IR spectroscopy and 2DCOS analysis showed different secondary structure forms under different ethanol concentrations at the isoelectric pH.For the hydration effect analysis,NIR spectroscopy combined with the McCabe-Fisher method and aquaphotomics showed that the free hydrogen-bonded water fluctuates dynamically,with ethanol at 0-20%enhancing the hydrogen-bonded water clusters,while weak hydrogen-bonded water clusters were formed when the ethanol concentration increased continuously from 20%to 30%.These measurements provide new insights into the structural changes and changes in the hydration behavior of HSA,revealing the dynamic process of protein purification,and providing a theoretical basis for the selection of HSA alcoholic precipitation process parameters,as well as for further studies of complex biological systems.

Chromatographic fingerprinting and quantitative analysis for the quality evaluation of Xinkeshu tablet

A simple, sensitive and accurate method based on high performance liquid chromatography (HPLC) with diode array detector (DAD) was developed and validated for systematic quality evaluation of one type of traditional Chinese medicine preparations named Xinkeshu (XKS) tablet. In this study, the chromatographic fingerprints of XKS tablet were developed first, 23 peaks were selected as the common peaks to evaluate the similarities among different batches of XKS samples, which were manufactured in a long time span of three years. Additionally, simultaneous quantification of six markers in XKS tablet, including Danshensu, Protocatechuic aldehyde, Puerarin, Daidzin, Salvianolic acid B and Daidzein, was performed. The validation results showed that the developed method was specific, accurate, precise and robust. The preliminary explanation on why a close similarity between fingerprints did not exactly mean similar contents of chemical components in samples was given. The contribution of each chromatographic peak to similarity was also evaluated. The developed method offers an efficient, reliable and practical approach for systematic quality evaluation of XKS tablet.

Deletion of a Non-Catalytic Region Increases the Enzymatic Activity of a β-Agarase from Flammeovirga sp. MY04

A Glycoside hydrolase(GH) typically contains one catalytic module and varied non-catalytic regions(NCRs). However, effects of the NCRs to the catalytic modules remain mostly unclear except the carbohydrate-binding modules(CBMs). Aga G4 is a GH16 endo-β-agarase of the agarolytic marine bacterium Flammeovirga sp. MY04. The enzyme consists of an extra sugar-binding peptide within the catalytic module, with no predictable CBMs but function-unknown sequences in the NCR, which is a new characteristic of agarase sequences. In this study, we deleted the NCR sequence, a 140-amino acid peptide at the C-terminus and expressed the truncated gene, aga G4-T140, in Escherichia coli. After purification and refolding, the truncated agarase r Aga G4-T140 retained the same catalytic temperature and p H value as r Aga G4. Using combined fluorescent labeling, HPLC and MS/MS techniques, we identified the end-products of agarose degradation by r Aga G4-T140 as neoagarotetraose and neoagarohexaose, with a final molar ratio of 1.53:1 and a conversion ratio of approximately 70%, which were similar to those of r Aga G4. However, the truncated agarase r Aga G4-T140 markedly decreased in protein solubility by 15 times and increased in enzymatic activities by 35 times. The oligosaccharide production of r Aga G4-T140 was approximately 25 times the weight of that produced by equimolar r Aga G4. This study provides some insights into the influences of NCR on the biochemical characteristics of agarase Aga G4 and implies some new strategies to improve the properties of a GH enzyme.

Spectra selection methods:A novel optimization way for treating dynamic spectra and in-line near infrared modeling

Near infrared(NIR)spectroscopy is now widely used influidized bed granulation.However,there are still some demerits that should be overcome in practice.Valid spectra selection during modeling process is now a hard nut to crack.In this study,a novel NIR sensor and a cosine distance method were introduced to solve this problem in order to make thefluidized process into"visualization".A NIR sensor wasfixed on the side of the expansion chamber to acquire the NIR spectra.Then valid spectra were selected based on a cosine distance method to reduce the influence of dynamic disturbances.Finally,spectral pretreatment and wavelength selection methods were investigated to establish partial least squares(PLS)models to monitor the mois-ture content.The results showed that the root mean square error of prediction(RMSEP)was 0.124%for moisture content model,which was much lower than that without valid spectra selection treatment.All results demonstrated that with the help of valid spectra selection treatment,NIR sensor could be used for real-time determination of critical quality attributes(CQAs)more accurately.It makes the manufacturing easier to understand than the process parameter control.

The relevance study of effective information between near infrared spectroscopy and chondroitin sulfate in ethanol precipitation process

Near infrared spectroscopy(NIRS)is based on molecular overtone and combination vibrations.It is difficult to assign specific features under complicated system.So it is necessary to find the relevance between NIRS and target compound.For this purpose,the chondroitin sulfate(CS)ethanol precipitation process was selected as the research model,and 90 samples of 5 different batches were collected and the content of CS was determined by modifed carbazole method.The relevance between NIRS and CS was studied throughout optical pathlength,pretreat ment methods and variables selection methods.In conclusion,the first derivative with Savitzky--Golay(SG)smoothing was selected as the best pretreatment,and the best spectral region was selected using interval partial least squares(iPLS)method under 1 mm optical cell.A multivariate cali-bration model was established using PLS algorithm for determining the content of CS,and the root mean square error of prediction(RMSEP)is 3.934gL-1.This method will have great potential in process analytical technology in the future.

Rapid determination of hyaluronic acid concentration in fermentation broth with near-infrared spectroscopy

Hyaluronic acid(HA)concentration is an important parameter in fermentation process.Cur-rently,carbazole assay is widely used for HA content determination in routine analysis.However,this method is time-consuming,environment polluting and has the risk of microbial contarmi-nation,as well as the results lag behind fermentation process.This paper attempted the feasibility to predict the concentration of HA in fermentation broth by using near infrared(NIR)spec-troscopy in transmission mode.In this work,a total of 56 samples of fermentation broth from 7 batches were analyzed,which contained HA in the range of 2.35-9.69 g/L.Diferent data pre-processing methods were applied to construct calibration models.The final optimal model was obtained with first derivative using Savitzky-Golay smoothing(9 points window,second-order polynomial)and partial least squares(PLS)regression with leave-one-block out CrOsS validation.The correlation cofficient and Root Mean Square Error of prediction set is 0.98 and 0.43 g/L,respetively,which show the possibility of NIR as a rapid method for microanalysis and to be a promising tool for a rapid assay in HA fermentation.

Application of near infrared spectroscopy in monitoring the moisture content in freeze-drying process of human coagulation factor VIII

As an important process analysis tool,near infrared spectroscopy(NIRS)has been widely used in process monitoring.In the present work,the feasibility of NIRS for monitoring the moisture content of human coagulation factor VIII(FVIII)in freeze-drying process was investigated.A partial least squares regression(PLS-R)model for moisture content determination was built with 88 samples.Different pre-processing methods were explored,and the best method found was standard normal variate(SNV)transformation combined with 1st derivation with Savitzky–Golay(SG)15 point smoothing.Then,four different variable selection methods,including uninformative variable elimination(UVE),interval partial least squares regression(iPLS),competitive adaptive reweighted sampling(CARS)and manual method,were compared for eliminating irrelevant variables,and iPLS was chosen as the best variable selection method.The correlation coe±cient(R),correlation coe±cient of calibration set(Rcal),correlation coefficient of validation set(Rval),root mean square errors of cross-validation(RMSECV)and root mean square errors of prediction(RMSEP)of PLS model were 0.9284,0.9463,0.8890,0.4986% and 0.4514%,respectively.The results showed that the model for moisture content determination has a wide range,good linearity,accuracy and precision.The developed approach was demonstrated to be a potential for monitoring the moisture content of FVIII in freeze-drying process.

Determination of the immunoglobulin G precipitation end-point by an intelligent near-infrared spectroscopy system

Precipitation is a key manufacturing unit during the immunoglobulin G(IgG)production,which guarantees the quality of the final product.Ethanol is usually used to purify IgG during the precipitation process,so it is important to monitor the ethanol concentration online.Near-infrared(NIR)spectroscopy is a powerful process analytical technology(PAT)which has been proved to be feasible to determine the ethanol concentration during the precipitation process.However,the NIR model is usually established based on the specific process,so a universal model is needed.And the clarity degree of solution will affect the quality of the spectra.Therefore,in this study an integrated NIR system was introduced to establish a universal NIR model which could predict the ethanol concentration online and determine the end-point of the whole process.First,a spectra acquisition device was designed and established in order to get high-quality NIR spectra.Then,a simple prepared ethanol NIR model was constructed to predict the actual manufacturing process.Finally,the end-point was determined to stop the peristaltic pump when the ethanol concentration reached 20%.The results showed that the spectra quality was good,model prediction was accurate,and process monitoring was accurate.In conclusion,all results indicated that the integrated NIR system could be used to monitor the biopharmaceutical process to help us understand the pharmaceutical process.

Chemical Synthesis of an Octasaccharide Derivative Related to Group B Streptococcus Cell-Wall Polysaccharide

Group B Streptococcus(GBS)is the major pathogen that causes invasive infectious diseases in neonates and infants.The develop-ment of preventive and therapeutic strategies against GBS infection has been becoming the most pressing subject worldwide.Group B carbohydrate(GBC),the group B-specific polysaccharide that distinguishes GBS with other streptococci species,has been identified as an attractive antigen for diagnosis and vaccine development because of its highly conservative tetra-antennary structure.In this paper,a highly convergent[3+5]glycosylation strategy for efficient synthesis of an octasaccharide derivative related to GBC oligo-saccharide unitⅡhas been developed.In this synthesis,each glycosylation reaction was efficiently constructed with glycosyl im-idates,especially trifluoroacetimidate,as donors,and each glycosidic bond was stereoselectively controlled via the neighboring group participation effect of acyl group on the 2-O-position of imidate donors or the solvent effect of Et_(2)O.Furthermore,the ami-noethylphosphate group was smoothly installed on the 6-O-position of D-glucitoll residue using the phosphoramidite method.After global deprotection,the target octasaccharide was successfully obtained from o-glucitol in 29 steps with an overall yield of 1.37%.The free amino group installed on the aminoethylphosphate spacer of the target molecule enables its modification with functional-ized biomolecules for further biological studies.

Stereoselective synthesis of the 3,6-branched Fuziα-glucans up to 15-mer via a one-pot and convergent glycosylation strategy

A family of the 3,6-branched Fuziα-glucans including the pentasaccharide repeating unit as well as its di-and trimers were efficiently achieved via a one-pot and convergent glycosylation strategy.All the protectedα-glucans up to 15-mer were assembled with high yields and excellentα-stereoselectivity,which was secured by the synergisticα-directing effects of the Tol SCl/Ag OTf promotion system and the stericβ-facial shielding of bulky saccharide residues linked at the 6-O-position of glucosyl donors.Moreover,the 3,6-branched architecture of glycosyl donor was revealed to be more favorable for theα-selective glucosidation of primary hydroxyl group,especially in the case of large oligosaccharide acceptor.The structurally well-defined syntheticα-glucans would be useful for various biological studies.

Stereodirecting Effects of 4-O-ortho-cyanobenzyl Ether on Chemical Glycosylation with Glucopyranosyl Donor

Here we report a systematic investigation on the stereodirecting effects of a 4-O-ortho-cyanobenzyl ether(oBCN)group with a glucopyranosyi donor.Experimental studies revealed that the glycosylation reactions using this donor generally show dual-stereoselectivities depending on the acceptor nucleophilicity,that is,glycosylation of weak nucleophile acceptors generally affordsα-glycosides specifically while glycosylation of strong nucleophile acceptors affords β-glycosides preferentially.

Late-stage cascade of oxidation reactions during the biosynthesis of oxalicine B in Penicillium oxalicum

Oxalicine B(1)is an a-pyrone meroterpenoid with a unique bispirocyclic ring system derived from Penicillium oxalicum.The biosynthetic pathway of 15-deoxyoxalicine B(4)was preliminarily reported in Penicillium canescens,however,the genetic base and biochemical characterization of tailoring reactions for oxalicine B(1)has remained enigmatic.In this study,we characterized three oxygenases from the metabolic pathway of oxalicine B(1),including a cytochrome P450 hydroxylase OxaL,a hydroxylating Fe(II)/a-KG-dependent dioxygenase OxaK,and a multifunctional cytochrome P450 OxaB.Intriguingly,OxaK can catalyze various multicyclic intermediates or shunt products of oxalicines with impressive substrate promiscuity.OxaB was further proven via biochemical assays to have the ability to convert 15-hydroxdecaturin A(3)to 1 with a spiro-lactone core skeleton through oxidative rearrangement.We also solved the mystery of OxaL that controls C-15 hydroxylation.Chemical investigation of the wild-type strain and deletants enabled us to identify 10 metabolites including three new compounds,and the isolated compounds displayed potent anti-influenza A virus bioactivities exhibiting IC50values in the range of 4.0-19.9μmol/L.Our studies have allowed us to propose a late-stage biosynthetic pathway for oxalicine B(1)and create downstream derivatizations of oxalicines by employing enzymatic strategies.

Identification and activity evaluation of Astragalus Radix from different germplasm resources based on specific oligosaccharide fragments

Objective: Based on trifluoroacetic acid(TFA) hydrolysis, polyacrylamide gel electrophoresis(PAGE) and high performance thin layer chromatography(HPTLC) analysis, the carbohydrate responsible for immunomodulatory activity are used as quality indicators for Astragalus Radix(AR).Methods: In this study, 24 batches of AR from different germplasm resources were selected as the research object, and AR polysaccharides were extracted. PAGE and HPTLC methods were used to analyze the partial acid hydrolyzate of AR polysaccharides and obtain a series of saccharide fingerprints. The data were analyzed by principal component analysis to obtain the difference between AR from different germplasm resources.Results: The results showed that trisaccharide and tetrasaccharide could be used as differential fragments to distinguish AR of different cultivation methods;Disaccharides and trisaccharides can be used as differential fragments to distinguish different species of AR. The immunological activity analysis of the specific oligosaccharide fragment of AR showed that the specific oligosaccharide fragment of AR could promote the secretion of TNF-α, IL-1β, IL-6, and NO in THP-1 cells in a concentration-dependent manner.Conclusion: Both PAGE and HPTLC methods can be used to evaluate AR from different germplasm resources. This study laid the foundation for the quality evaluation of AR medicinal herbs.

Enzyme-like C-H Oxidation of Glucosides Promoted by Visible Light

To match nature’s prowess at using enzymes to make desired motifs in a regioselective fashion,we explore the use of visible light for the selective oxidation of the hydroxyl group to afford the corresponding ketosaccharide.This highly admirable approach offers several advantages over the enzymatic approach in terms of yields and the scope of substrates.Herein,we report the development of a simple visiblelight-promoted selective oxidation of unprotected glucosides that allows for inexpensive access to valuable keto-saccharide building blocks.The method is employed on a variety of different natural and artificial glucosides,is operationally simple and scalable,and can be used to access keto-saccharides rapidly and inexpensively.

Gut microbiota have blood types as human

ABO blood group system was firstly recognized by Landsteiner in 1900[1].Since then,the antigens of the ABO system (A,B and H determinants,respectively)have been shown to encompass complex carbohydrate structures [2].A and B antigen were synthesized by the sequential action of glycosyltransferases,with A and B glycosyltransferases catalyzing the addition of N-acetylgalactosamine and D-galactose to precursor H antigen,respectively. Group O individuals lack such transferase enzymes and consequently continue to express the basic H structure only [3,4].It is determined that approximate 2million ABH glycan antigen sites are presented on each red blood cell [5].Additionally,the ABH antigens are widely expressed in other human ceils and tissues,including the sensory neurons,epithelium,the vascular endothelium and platelets [6].

Stereodivergent synthesis of C-glycosamino acids via Pd/Cu dual catalysis

Herein,we reported the stereodivergent synthesis of C-glycosamino acids via Pd/Cu dual catalysis and found a suitable system to resolve many challenges,such as the tolerance towards the density of functional groups,the variability of the anomeric position,the compatibility of appropriate catalyst combinations,the regioselectivity of nucleophiles,and the match/mismatch problems between chiral substrates and chiral ligand-metal complexes.The method enables the efficient preparation of a series of unnatural C-glycosamino acid skeletons bearing two contiguous stereogenic centers in good yields with excellent diastereoselectivity.From this crucial precursor,various C-glycosamino acid derivatives have been achieved diversely.The readily prepared C-glycosamino acid hybrids will meet the growing demands for the development of new molecular entities for discovering new drugs and materials.This stereodivergent synthesis of C-glycosamino acids will further accelerate the study of their structural features,mode of action,and potential biological applications in the near future.

Sequential One-Pot Three-Enzyme Synthesis of the Tetrasaccharide Repeating Unit of Group B Streptococcus Serotype Ⅷ Capsular Polysaccharide

The biochemical property and functional identification of three recombinant glycosyltransferases,includingβ-1,4-rhamnosyltransferase(Cps8R),β-1,4-galactosyltransferase(Cps8) and α-2,3-sialyltransferase(Cps8K)involved in the biosynthesis of the tetrasaccharide repeating unit of serotypeⅧcapsular polysaccharide(CPS)of Group B Streptococci(GBS),were systematically investigated.Subsequently,these recombinant enzymes were employed for one-pot three-enzyme efficient synthesis of the tetrasaccharide repeating unit of GBS serotypeⅧCPS using the chemically synthesized Glca-PP-(CH2)ir-OPh as the starting substrate in a satisfying yieldof 87%.

Divergent Synthesis of Core m1,Core m2 and Core m3 O-Mannosyi Glycopeptides via a Chemoenzymatic Approach

O-Mannosylation plays a vital role in the regulation of a variety range of biological processes,for instance,brain and muscle development.However,the precise function remains largely unknown due to its innate heterogeneity.In this regard,it is still welcome to develop efficient methods to access diverse structurally-defined glycopeptides.In this study,a diversity-oriented assembly of O-mannosylα-dystroglycan(α-DG)glycopeptides has been achieved via a chemoenzymatic strategy.This strategy features(i)gram scale divergent synthesis of core m1,core m2 and core m3 mannosylated amino acids from judiciously designed protecting group strategies and chemical glycosidation;(i)efficient glycopeptide assembly via the optimized microwave-assisted solid phase peptide synthesis(SPpS);and(ii)enzymatic elaboration of the core glycan structures to install galactosyl and sialyl-galactosyl moieties.The efficiency and flexibility of this chemoenzymatic approach was demonstrated with the construction of 12 glycopeptides with different core m1,core m2 and core m3 mannosyl glycans,including a core m2 glycopeptide bearing a heptasaccharide for the first time.

A new strategy for high-throughput identification of human gut microbiota containing specific monosaccharide

Dear Editor,The human gastrointestinal tract is colonized by trillions of microorganisms,the majority of which cannot be cultured (Wu et al.,2018).Numerous glycans are expressed on the surface of gut microbiota that are characteristic of different strains,and the diversity of these glycans is partially attributed to variations in their monosaccharides.