Three anti-inflammatory polysaccharides from Lonicera japonica Thunb.:insights into the structure-function relationships

This study demonstrates the feasibility of producing three polysaccharides(neutral LJP-1,acidic LJP-2 and acidic LJP-3)with significant in vitro and in vivo anti-inflammatory activities from the flowers of Lonicera japonica.The three polysaccharides differed in chemical composition,molecular weight(Mw)distribution,glycosidic linkage pattern,functional groups and morphology.They exhibited excellent protective effects(in a dose-dependent manner)in lipopolysaccharide-injured RAW264.7 macrophages and Cu SO4-damaged zebrafish via reducing NO production and inhibiting the overexpressions of inflammation-related transcription factors,inflammatory proteins and cytokines in the NF-κB/MAPK signaling pathways.Their antiinflammatory effects varied owing to their different molecular characteristics and chemical compositions.Overall,LJP-2 at 400μg/m L was the most effective.LJP-2 consisted mainly of→5)-α-L-Araf(1→,→4)-α-LGalp A(1→and→2)-α-L-Rhap(1→residues with terminal T-β-D-Glcp.Thus,honeysuckle flowers are good sources of anti-inflammatory polysaccharides,and precise fractionation enables the production of potent antiinflammatory agents for the development of functional foods and healthcare products.

Structure-function Relationships in Human Hypoxanthine-guanine Phosphoribosyltransferase(HGPRT) by Random Mutagenesis

Hypoxanthine-guanine phosphoribosyltransferase （ HGPRT, EC 2.4.2.8） is a key enzyme of the purine salvage pathway, which allows recycling of purine bases into DNA and RNA. It is widely distributed in nature and has been studied both in prokaryotes and eukaryotes. In humans, a complete lack of HGPRT activity causes the Lesch-Nyhan syndrome, which is characterized by hyperuricaemia and neural disorders,

Structure-function relationship of antimicrobial peptide cathelicidin Pc-CATH1

Cathelicidin Pc-CATH1 is a cathelicidin-derived myeloid antimicrobial peptide identified from Phasianus colchicus with strong antimicrobial activity against most of bacteria and fungi tested,including the clinically isolated(IS)drug-resistant strains.Considering the uniform distribution of net positive charge in both C-and N-terminus sequence of cathelicidin Pc-CATH1 and most of hydrophobic amino acid(aa)residues positioned in middle of the sequence,the antimicrobial peptide was used to investigate the structure-function relationship by truncating gradually N-or C-terminus amino acid residue.More than 10 modified peptide homo-logues(20-26 aa length)of cathelicidin Pc-CATH1 were found to keep strong antimicrobial abilities.The possible relationships between bioactivities including antimicrobial and hemolytic abilities,components of secondary structure,hydrophobicity,amphipathicity,net charge,and sequence length were investigated.The current work provided suggestions for structural and functional modification of linear,α-helical antimicrobial peptides containing no disulfided bridges.

Variations in Phytic Acid Content and Their Relationship with Protein Content and Kernel Morphological Characters of Chinese Winter Wheat Cultivars

[Objective] The aim of this study was to determine the variation of phytic acid content （PAC） and its frequency distribution, as well as the relationship between PAC and protein content, kernel characteristics in 161 Chinese winter wheat cultivars from four regions. [Method] One hundred and sixty-one winter wheat varieties from China Wheat Zones I, II, III and IV （Table 1） were grown in a randomized block de- sign, in the 2009-2011 cropping season; and then the indexes for describing the grain morphological characteristics such as the thousand kernel weight （TKW）, kernel length （KL）, kernel width （KW） and kernel thickness （KT） were measured; the phytic acid content （PAC）, protein content and sedimentation value were also determined; finally, the relationship between PAC and protein content, kernel characteristics were analyzed. [Result] The PAC in the cultivars tested ranged from 0.92% to 1.95% with a mean value of 1.41%. Protein content ranged from 12.60% to 19.20%, with a mean of 15.24%. Most （53.4%） of the wheat genotypes had a PAC value in the range of 1.25% to 1.55%. No significant correlation was found between PAC and protein content, sedimentation value, while protein content and SDS sedimentation value was significant correlated, which suggested the possibility of breeding wheat cultivars that have a low PAC but a high protein content and good gluten quality. There was a high correlation between TKW and KW （,.=0.79）, KL （r=0.50） and KT （r=0.64）. PAC was found having no significant correlation with TKW, KW, KL and KT. [Conclusion] The result suggests the possibility of breeding wheat cultivars that have a low PAC but high kernel weight.

PHYLETIC RELATIONSHIP OF PROTEIN STRUCTURES BASED ON SPATIAL PREFERENCE OF RESIDUES

A distance measure that infers to indicate the evolutionary relationship of protein structures has been developed based on spatial preference factors of residues. The spatial preference factor is a reflection of the environment of residues in tertiary structure. Compared with the phyletic relationships derived from sequence homologies and three-dimensional structures, we find that the two lines of evolution are similar in general. This approach is applied to a group of glins here.

腹膜透析患者血清klotho蛋白水平与中医证候的相关性研究

目的:探讨腹膜透析患者血清klotho蛋白水平与中医证候的相关性。方法:选取180例规律腹膜透析患者作为研究对象,均进行中医辨证,分为主证和兼证两类;并根据患者肾小球滤过率(GFR)和血清分泌型klotho蛋白水平的四分位数,分为4组,统计各组中医主证、兼证分布情况。结果:180例腹膜透析患者主证占比,脾肾气虚证>气阴两虚证>肝肾阴虚证>脾肾阳虚证>阴阳两虚证;兼证占比,瘀血证>湿热证>湿浊证;不同主证的GFR和klotho蛋白水平存在显著性差异(P<0.05),GFR、klotho蛋白水平比较,肝肾阴虚证<阴阳两虚证<气阴两虚证<脾肾阳虚证<脾肾气虚证,且GFR与血清klotho蛋白水平呈正相关。不同兼证患者GFR和klotho蛋白水平比较无统计学意义(P>0.05)。按照血清分泌型klotho蛋白水平分布范围分组,发现在klotho蛋白水平较低的患者中,肝肾阴虚证和阴阳两虚证的占比较高;相反,在klotho蛋白水平较高的患者中,脾肾气虚证和脾肾阳虚证的占比较高,各组中医主证比率比较有统计学意义(P<0.05),而兼证比率比较无统计学意义(P>0.05)。结论:腹膜透析患者血清klotho蛋白水平与中医主证呈显著相关性,且肝肾阴虚证、阴阳两虚证者klotho蛋白降低尤其明显,主要与肾精不足或衰退相关。

核桃炭疽病菌中GH互作蛋白找寻及遗传关系分析

【目的】植物病原真菌中的糖苷水解酶(GH)是参与破坏植物细胞壁的重要酶类,在真菌致病过程中发挥着重要作用。了解核桃炭疽病菌中GH蛋白的互作蛋白及其遗传关系,可为深入研究该病菌中GH家族蛋白的协同作用机制提供参考。【方法】基于前期所获得的胶孢炭疽菌Cg1中20个GH蛋白,通过STRING网络在线分析与其相似性较高的两个炭疽菌种——胶孢炭疽菌Cg-14和果生炭疽菌Nara gc5相关蛋白的互作关系;同时,利用生物信息学分析工具对这些蛋白进行了分子对接、亚细胞定位及遗传关系分析。【结果】两个炭疽菌菌株GH蛋白的互作情况极为相似。其中:GH5的互作蛋白数量最多,且GH5、GH6、GH7、GH11之间均存在明显互作关系;GH28亚家族中两个蛋白之间互作但不与其他GH亚家族蛋白互作;与单独GH蛋白存在互作关系的其他类蛋白多参与多糖催化、碳水化合物代谢等过程。不同蛋白之间均存在多个相互作用的氨基酸位点;仅GH72亚家族中的3个蛋白定位于质膜,其余蛋白均定位于细胞外;胶孢炭疽菌Cg1、Cg-14以及果生炭疽菌Nara gc5中GH蛋白明显分为四大类。其中:GH43亚家族中的3个蛋白分属于不同分支,亲缘关系较远;GH5中的3个蛋白有两个属于同一分支,另一个单独在一个分支;而GH7、GH11、GH28亚家族内部的蛋白均属于同一分支。【结论】核桃炭疽病菌中GH蛋白的互作关系主要有3种,即不同GH蛋白之间的互作、同一GH亚家族中不同蛋白之间的互作以及单独的GH蛋白。其中,大部分GH蛋白定位于细胞外,且大多数GH亚家族中不同蛋白之间的亲缘关系较近,仅有小部分亲缘关系较远。

辣椒小G蛋白CaROP的生物信息学分析

【目的】研究辣椒内小G蛋白CaROP的生物学功能、蛋白理化性质、蛋白结构及系统发育关系。【方法】运用ProtParam、ProtScale、SignalP5.0、TMHMM、NetPhos3.1和NetCGlyc1.0等生物信息学软件分析9个CaROP蛋白的蛋白理化特性;运用SOPMA和SWISS-MODEL等生物信息学软件预测分析9个CaROP蛋白的结构;运用生物信息学软件MEGA11分析9个CaROP蛋白的系统发育关系。【结果】9个CaROP蛋白的亲水性总平均值均小于0,均为亲水蛋白,其中6个为稳定的亲水蛋白;9个CaROP蛋白均无信号肽,即均为非分泌性蛋白;9个CaROP蛋白无跨膜结构域,即均非膜蛋白;9个CaROP蛋白均存在磷酸化位点,均无糖基化位点。9个CaROP蛋白的主要二级结构原件为无规则卷曲和α-螺旋,其次是β-折叠,最后是β-转角。9个CaROP蛋白聚为4个分支,其中分支Ⅰ和分支Ⅲ各包括1个CaROP蛋白。分支Ⅱ包括2个CaROP蛋白,其余5个CaROP蛋白均聚于分支Ⅳ中。【结论】9个CaROP蛋白具有完整的Rho功能域,均为非分泌性亲水蛋白。9个CaROP蛋白在系统进化树中共聚为了4个分支,其三级结构建模的预测结果也均较为理想,9个CaROP蛋白结构较稳定。

2型糖尿病患者血清C1q肿瘤坏死因子相关蛋白5、脂联素水平与颈动脉粥样硬化关系研究

目的:探讨2型糖尿病(T2DM)患者血清C1q肿瘤坏死因子相关蛋白5(CTRP5)、脂联素(APN)水平与颈动脉粥样硬化(CAS)的关系。方法:选择T2DM患者96例为观察组,选择体检健康者108例为对照组。采用酶联免疫吸附(ELISA)法检测血清CTRP5、APN水平。根据超声检查将T2DM患者分为CAS组和无CAS组,并比较两组一般资料及血清生化指标。分析T2DM患者发生CAS的影响因素,并进行相关性分析。结果:观察组血清CTRP5水平高于对照组,APN水平低于对照组(均P<0.05)。T2DM患者中,40例出现CAS,56例无CAS。CAS组患者年龄、空腹血糖(FPG)、糖化血红蛋白(HbA1c)、甘油三酯(TG)、高密度脂蛋白胆固醇(HDL-C)、低密度脂蛋白胆固醇(LDL-C)、CTRP5水平较无CAS组升高,APN水平较无CAS组下降(均P<0.05)。HbA1c、TG、LDL-C、CTRP5为CAS发生的独立危险因素,APN是CAS的独立保护因素(均P<0.05)。血清CTRP5与HbA1c、TG、LDL-C水平呈正相关,血清APN与HbA1c、TG、LDL-C水平呈负相关(均P<0.05)。结论:T2DM患者发生CAS后CTRP5水平升高,APN水平下降,CTRP5为CAS发生的独立危险因素,APN为CAS发生的独立保护因素。

红豆肽的制备、分离纯化及降糖活性研究

目的:筛选红豆蛋白的酶解工艺并研究红豆多肽的降糖活性及构效关系。方法:采用碱沉酸提法提取红豆粗蛋白,以肽得率、水解度、α-葡萄糖苷酶抑制、Fe^(2+)螯合率、DPPH清除率为指标筛选最佳蛋白酶;酶解得到红豆多肽,醇沉多糖后通过DA201-C大孔吸附树脂进行脱盐纯化后,测定多肽的分子量及氨基酸组成来探讨其构效关系。结果:经4种蛋白酶(中性、碱性、风味、复合蛋白酶)水解后,碱性蛋白酶的肽得率为82.95%,水解度为52.67%,实验浓度范围内最佳α-葡萄糖苷酶抑制为72.14%,比其他3种酶均高;85%乙醇醇沉后的肽糖比、α-葡萄糖苷酶抑制率(73.49%)和α-淀粉酶抑制率(31.31%)均最高,脱盐纯化后肽含量高达97.61%,在2 mg/mL时测定对α-葡萄糖苷酶和α-淀粉酶抑制效果,分别为52.49%和14.63%,表明除去多糖后红豆多肽仍具有独立降血糖活性;经测定,红豆多肽以小分子为主,3 kDa以下占比91.40%,其中小于1000 Da占比达到75.28%。纯化后疏水性氨基酸占比约37.28%,其中甘氨酸、丙氨酸、脯氨酸和谷氨酸含量较高。结论:碱性蛋白酶是制备红豆多肽的最佳蛋白酶,分离纯化后的红豆多肽具有降糖活性,其活性可能与4种疏水性氨基酸含量较高且分子量较小有关。

Extending the solid solution range of sodium ferric pyrophosphate:Off‐stoichiometric Na_(3)Fe(2.5)(P_(2)O_(7))_(2)as a novel cathode for sodium‐ion batteries

Iron‐based pyrophosphates are attractive cathodes for sodium‐ion batteries due to their large framework,cost‐effectiveness,and high energy density.However,the understanding of the crystal structure is scarce and only a limited candidates have been reported so far.In this work,we found for the first time that a continuous solid solution,Na_(4−α)Fe_(2+α)_(2)(P_(2)O_(7))_(2)(0≤α≤1,could be obtained by mutual substitution of cations at center‐symmetric Na3 and Na4 sites while keeping the crystal building blocks of anionic P_(2)O_(7) unchanged.In particular,a novel off‐stoichiometric Na_(3)Fe(2.5)(P_(2)O_(7))_(2)is thus proposed,and its structure,energy storage mechanism,and electrochemical performance are extensively investigated to unveil the structure–function relationship.The as‐prepared off‐stoichiometric electrode delivers appealing performance with a reversible discharge capacity of 83 mAh g^(−1),a working voltage of 2.9 V(vs.Na^(+)/Na),the retention of 89.2%of the initial capacity after 500 cycles,and enhanced rate capability of 51 mAh g^(−1)at a current density of 1600 mA g^(−1).This research shows that sodium ferric pyrophosphate could form extended solid solution composition and promising phase is concealed in the range of Na_(4−α)Fe_(2+α)_(2)(P_(2)O_(7))_(2),offering more chances for exploration of new cathode materials for the construction of high‐performance SIBs.

血浆蛋白与骨质疏松症的关系及潜在治疗靶点:基于国际UK Biobank数据库信息

背景:骨质疏松症是全球范围内增加疾病负担和致残率的重要因素。血浆蛋白参与体内复杂的生物过程,在揭示疾病机制和发现潜在治疗靶点方面起着关键作用。尽管已有研究显示血浆蛋白与骨质疏松症之间存在关联,但这些关联的因果性质尚未得到充分阐明。因此,利用大规模的血浆蛋白数据探究与骨质疏松症相关的因果蛋白并识别潜在的药物靶点,对于骨质疏松症的防治至关重要。目的:运用两样本孟德尔随机化分析,以国际UK Biobank数据库为来源信息,评估血浆蛋白与骨质疏松症之间的因果关联。方法:从UK Biobank数据库获取1001种血浆蛋白相关的全基因组显著性水平(P<5×10-8)的蛋白质数量性状位点作为工具变量,并排除连锁不平衡。骨质疏松症的汇总数据来自FinnGen数据库,共涉及438872名欧洲血统个体。研究采用逆方差加权、MR-Egger回归、加权中位数等方法进行分析,并进行多项敏感性分析以确保结果的稳健性。进一步构建蛋白-蛋白互作网络,结合基因本体富集分析和京都基因与基因组百科全书通路分析,探索血浆蛋白的功能相关性及潜在作用机制。结果与结论:①孟德尔随机化逆方差加权法结果显示有50种血浆蛋白与骨质疏松症存在因果关系(P<0.05),包括染色体19开放阅读框12(chromosome 19 open reading frame 12,C19orf12;OR=0.610,95%CI:0.483-0.769,P=2.967×10-5)、表皮生长因子(OR=0.877,95%CI:0.770-0.999,P=0.049)等20种血浆蛋白可能与骨质疏松症的风险降低相关,有CCL18(OR=1.091,95%CI:1.037-1.147,P=0.001)、CD209(OR=1.036,95%CI:1.003-1.070,P=0.034)等30种血浆蛋白可能增加骨质疏松症的风险,经Bonferroni校正后,只有C19orf12与骨质疏松症存在显著的因果关联。②多项敏感性分析显示研究不存在多效性和异质性,说明结果具有稳健性。③通过构建蛋白-蛋白互作网络明确了表皮生长因子、CCL5、CXCL13、CXCL5、血管内皮生长因子C、CCL18、CCL17、TEK受体酪氨酸激酶、含免疫球蛋白样和表皮生长因子样结构域的酪氨酸激酶1(TIE1)和CCL23为核心蛋白。④基因本体富集分析和京都基因与基因组百科全书通路分析表明这些血浆蛋白在免疫系统中具有重要作用,通过参与信号传导、细胞迁移和趋化等过程影响骨质疏松症。⑤文章结果揭示了1001种血浆蛋白与骨质疏松症的潜在因果关联,这种基于大规模数据驱动的分析方法有助于在中国人群中识别新的生物标志物和药物靶点;其次,文章结果表明,免疫系统信号传导、细胞迁移和趋化等过程在骨质疏松症发病机制中发挥重要作用,这为特定遗传背景和环境因素下的骨质疏松症研究提供了新的方向;最后,研究中识别的核心蛋白(如表皮生长因子、CCL5及CXCL13等)有望成为新的生物标志物或药物靶点,为骨质疏松症的精准防治提供新的依据。

食源性蛋白衍生钙与螯合肽构效关系研究进展

钙摄入不足会导致骨质疏松等症状,因此肽-钙螯合物作为新一代优良的补钙剂受到广泛关注。食品蛋白衍生的钙螯合肽因其广泛的来源和卓越的性能而具有独特的优势。本综述总结了不同动物来源、水生资源以及植物来源的钙螯合肽,并重点分析了肽的分子量、氨基酸序列和位置、特定氨基酸基团以及肽的空间结构等对肽与钙结合能力的影响。通过探讨肽与钙螯合的构效关系,旨在深入理解肽与钙之间的相互作用机制,并开发出更优质、高钙结合力的新型补钙剂产品。

Molecular characteristics and structure–activity relationships of food-derived bioactive peptides

Peptides are functional active fragments of proteins which can provide nutrients needed for human growth and development,and they also have unique physiological activity characteristics relative to proteins.Bioactive peptides contain a great deal of development potential.More specifically,food-derived bioactive peptides have the advantages of a wide variety of sources,unique structures,high efficiency and safety,so they have broad development prospects.This review provides an overview of the current advances regarding the preparation,functional characteristics,and structure–activity relationships of food-derived bioactive peptides.Moreover,the prospects for the future development and application of food-derived bioactive peptides are discussed.This review may provide a better understanding of foodderived bioactive peptides,and some constructive inspirations for further research and applications in the food industry.

The intracellular mechanism of alpha-fetoprotein promoting the proliferation of NIH 3T3 cells

AIM: The existence and properties of alpha-fetoprotein (AFP) receptor on the surface of NIH 3T3 cells and the effects of AFP on cellular signal transduction pathway were investigated. METHODS: The effect of AFP on the proliferation of NIH 3T3 cells was measured by incorporation of 3H-TdR. Receptor-binding assay of 125I-AFP was performed to detect the properties of AFP receptor in NIH 3T3 cells. The influences of AFP on the [cAMP]i and the activities of protein kinase A (PKA) were determined. Western blot was used to detect the change of K-ras P21 protein expression. RESULTS: The proliferation of NIH 3T3 cells treated with 0-80 mg/L of AFP was significantly enhanced. The Scatchard analysis indicated that there were two classes of binding sites with KD of 2.722 x 10(-9)M (Bmax=12810 sites per cell) and 8.931 x 10(-8)M (Bmax=119700 sites per cell) respectively. In the presence of AFP (20 mg/L), the content of cAMP and activities of PKA were significantly elevated . The level of K-ras P21 protein was upregulated by AFP at the concentration of 20 mg/L. The monoclonal antibody against AFP could reverse the effects of AFP on the cAMP content, PKA activity and the expression of K-ras p21 gene. CONCLUSION: The effect of AFP on the cell proliferation was achieved by binding its receptor to trigger the signal transduction pathway of cAMP-PKA and alter the expression of K- ras p21 gene.

Difference of Phytic Acid Content and its Relation to Four Protein Composition Contents in Grains of Twenty-nine japonica Rice Varieties from Jiangsu and Zhejiang Provinces,China

Twenty-nine japonica rice varieties collected from Jiangsu and Zhejiang Provinces, China were planted in Hangzhou, China, to investigate the phytic acid content in brown rice and its frequency distribution as well as the correlation among the contents of phytic acid, total protein and four protein compositions in brown rice. The phytic acid content in brown rice ranged from 0.699% to 1.034%, with a mean of 0.868% for the 29 tested rice varieties. Xiushui series rice varieties generally exhibited lower phytic acid level than Wuyujing and Huai series rice varieties. A rough normal distribution, with a mean of 8.722%, was observed for the total protein contents in the tested varieties. Of the four protein compositions, the glutelin, globulin and albumin contents had larger coefficient of variation than the prolamin content, although the difference in prolamin content was genotype-dependent. No significant correlation was found between the phytic acid and four protein composition contents, whereas the total protein content was significantly and positively related to the glutelin content in brown rice.

Protein structural codes and nucleation sites for protein folding

One of the long-standing controversial arguments in protein folding is Levinthal＇s paradox. We have recently proposed a new nucleation hypothesis and shown that the nucleation residues are the most conserved sequences in protein. To avoid the complicated effect of tertiary interactions, we limit our search for structural codes to the nucleation residues. Starting with the hypotheses of secondary structure nucleation and conservation of residues important for folding, we have analysed 762 folds classified as unique by SCOP. Segments of 17 residues around the top 20% conserved amino acids are analysed, resulting in approximately 100 clusters each for the main secondary structure classes of helix, sheet and coil. Helical clusters have the longest correlation range, coils the shortest （four residues）. Strong specific sequence-structure correlation is observed for coil but not for helix and sheet, suggesting a mapping relationship between the sequence and the structure for coil. We propose that the central sequences in these clusters form ＇structural codes＇, a useful basis set for identifying nucleation sites, protein fragments stable in isolation, and secondary structural patterns in proteins （particularly turns and loops）.

Disorder structural predictions of the native EWS and its oncogenic fusion proteins in rapport with the function

The Intrinsic structural disorder (ISD) of native EWS and its fusion oncogenic proteins, including EWS/FliI, EWS/ATF1 and EWS/ZSG, was estimated by different Predictors. The ISD difference between the wild type and the oncogenic fusions found in the CTD is due to the fusion partner, usually a transcription factor (TF). A disordered region was found in the sequence (AA 132 - 156) of the NTD (EAD) of EWS, consisting of the longest region free of Y motifs. The IQ domain (AA 258 - 280), a Y-free region, flanked by two Y-boxes, is also disordered by all used Predictors. The EWS functional regions RGG1, RGG2 and RGG3 are predominantly disordered. A strong dependence was found between the structure of EWS protein and its oncogenic fusions, and their estimated ISD. The oncogenic function of the fusions is related to a decreased ISD in the CTD, due to the fused TF. The Predictors shown that the different isoforms have similar profiles, shifted with some amino acids, due to the translocations. On the bases of the prediction results, an analysis was made of the EWS sequence and its functional regions with increased ISD to make a relationship sequence-disorder-function that could be helpful in the design of antitumor agents against the corresponding malignances.

Structure-activity relationships regarding the antioxidant effects of the flavonoids on human erythrocytes

The effects of eleven flavonoids on lipid peroxidation, protein degradation, deformability and osmotic fragility of human erythrocytes exposed in vitro to 10 mM H2O2 for 60 min at 37 oC have been studied. The following flavonoids;quercetin, rutin and morin significantly protected eryt-hrocytes against lipid peroxidation caused by H2O2. This inhibition of lipid peroxidation could be explained by the presence of at least two hydroxyl groups in ring B of the flavonoid structure, regardless of their positions. However, the flavonoids;quercetin, 3,5,7-trihy- droxy-4'-methoxy flavone-7-rutinoside and 3- hydroxy flavone significantly protected eryt-hrocytes against protein degradation. This inhibition could also be explained by the presence of a hydroxyl group at C-3 in ring C of the flavonoid structure. Quercetin and 3,5,7-trihydroxy-4'- methoxy flvone-7-rutinoside significantly protected erythrocytes against loss of deformability and increased osmotic fragility, indicating that the loss of erythrocyte deformability and the increase in osmotic fragility of erythrocytes exposed to H2O2 are related to protein degradation rather than to lipid peroxidation. The other flavonoids (chrysin, 2-carboxy ethyl dihydroxy flavone, apigenin, cirsimaritin, α-naphto flavone and flavanone) failed to protect erythrocytes against the observed oxidative damages. The results demonstrate the importance of the chemical groups substituted on the basic skeleton of the flavonoids in dictating the type of antioxidant activity, and also demonstrate the hemorheological potentials of flavonoids that have particular protein-antioxidant activities.

Structure-activity correlationship and folding of recombinant Escherichia coli dihydro folate reductase (DHFR) enzyme through biochemical and biophysical approaches

The design of any antagonist or inhibitor for any enzyme requires the knowledge of structure- function relationship of the protein and the optimum conformational states for maximum and minimum activities. Furthermore, designing of the inhibitors or drugs against an enzyme becomes easier if there is information available about various well characterized intermediate conformation of the molecule. In vivo folding pathway of any recombinant protein is an important parameter for understanding its ability to fold by itself inside the cell, which always dictates the downstream processing for the purification. In the present manuscript we have discussed about the in vivo and in vitro folding, and structure-function relationship of Dihydrofolate reductase enzyme. This is an important enzyme involved in the cell growth and hence inhibition or inactivation of the enzyme may reduce the cell growth. It was observed that the equilibrium unfolding transition of DHFR proceeds through the formation of intermediates having higher exposed surface hydrophobicity, unchanged enzymatic activity and minimum changes in the secondary structural elements. Because of enhanced surface hydrophobicity, and unchanged enzymatic activity, these intermediates could be a nice target for designing drugs against DHFR.