A Novel Polypeptide from Cervus elaphus Linnaeus

A novel polypeptide having stimulant effect on some cell proliferation was isolated from the velvet antler (Cervus elaphus Linnaeus). The velvet antler polypeptide consists of a single chain of 32 amino acid residues. Amino acid sequence of the polypeptide was identified as:VLSAADKSNVKAAWGKVGGNAPAFGAEALLRM.     

A Novel Peptide from Buthus martensii Karch

A novel peptide was purified and characterized from Buthus martensii Karch.The peptide,named BmK M6,is a single-chain polypeptide cross-linked by four intramolecular disulfide bridges.The molecular weight of the peptide was determined by MOLDI-TOF-MS as 7034 Da.The partial amino acid sequence of BmK M6 from N-terminal is VRDAYIAKPEN CVYECGITQDCNKLCTENG.     

Sequence pattern Correlation of Amino Acid in Collision—induced Dissociation Electrospray Ionization Mass Spectrometry

A novel approach of seuqence pattern correlation has been applied to predict an expected amino acid sequence from CID ESI-MS spectra.The proposed approach deduces sequence patterns with no help form known protein database such that it is useful to identify an unknown petide or new protein.The algorithm applies a cross-correlation to match an experimental CID spectrum with predicted sequence pattern generated form fragmentation information.The fragmentation knowledge of both y-series and other non y-series are utilized to generate the predicted sequence patterns.In contrast to the normal de novo approach,the proposed approach is insensitive to mass tolerance and non-sussceptive to spectral integrality with no need for selection of a starting point.     

蚕丝纤维增强聚乳酸体系中柱晶的形成及结构分析

采用溶液法制备聚乳酸(PLA)薄膜,并利用偏光显微镜在线研究了不同温度及不同牵引速率下,单根蚕丝纤维(SF)诱导PLA柱晶的形成,并利用显微红外光谱表征柱晶结构.结果表明,当牵引速率大于或等于临界速率时,纤维表面有连续的柱晶生成,反之柱晶不连续;当牵引速率大于临界饱和速率时,柱晶的结晶度和取向度分别趋于稳定值;在等温条件下,随着牵引速率的增大,柱晶的成核诱导期缩短,晶体的成核密度增大,取向度增加;当牵引速率一定时,与130℃相比,温度为120℃时形成柱晶的成核诱导期较短,成核密度更大,结晶度更高,柱晶层的生长更快.     

Characterization of Peanut Protein Hydrolysate and Structural Identification of Umami-Enhancing Peptides

Umami peptides are naturally found in various foods and have been proven to be essential components contributing to food taste. Defatted peanut powder hydrolysate produced by a multiprotease (Flavorzyme, Alcalase, and Protamex) was found to elicit an umami taste and umami-enhancing effect. The taste profiles, hydrolysis efficiency, amino acids, molecular weight distribution, Fourier transform infrared spectroscopy (FT-IR), and separation fractions obtained by ultrafiltration were evaluated. The results showed that peanut protein was extensively hydrolyzed to give mainly (up to 96.84%) free amino acids and peptides with low molecular weights (<1000 Da). Furthermore, β-sheets were the major secondary structure. Fractions of 1–3000 Da and <1000 Da prominently contributed to the umami taste and umami enhancement. To obtain umami-enhancing peptides, these two fractions were further purified by gel filtration chromatography, followed by sensory evaluation. These peptides were identified as ADSYRLP, DPLKY, EAFRVL, EFHNR, and SDLYVR by ultra-performance liquid chromatography (UPLC), and had estimated thresholds of 0.107, 0.164, 0.134, 0.148, and 0.132 mmol/L, respectively. According to the results of this work, defatted peanut powder hydrolysate had an umami taste and umami-enhancing effect, and is a potential excellent umami peptide precursor material for the food industry.     

Design,Synthesis and Characterization of A Novel Cationic Polymer Poly(lactic acid-b-L-lysine)

A novel biodegradable block copolymer poly(lactic acid-b-lysine) (PLA-b-PLL) has been synthesized and characterized in this study. This product was synthesized via a five-step reaction: Synthesis of hydroxyl-tailed poly(lactic acid) (PLA) by the ring-opening polymerization (ROP) of D,L-lactide in the presence of stannous octoate (Sn(OCt)₂) as initiator; coupling N-t-butoxycarbonyl-L-phenylalanine to hydroxyl-tailed PLA using dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP); the amino-tailed PLA was obtained through de-protection of the Boc-protective group in trifluoroacetic acid (TFA) solution; and then ring-opening polymerization of N ^ε -(Z)-lysine-N-carboxyanhydride (NCA) using the amino-tailed PLA as macro-initiator; finally removal of the Cbz-protective group of PLA-b-poly(N ^ε -(Z)-L-lysine) (PLA-b-PLL(Z) in a mixed hydrobromic acid/acetic acid solution to give the target copolymer. The characterization of this copolymer and its precursors were performed by ¹H-NMR, FTIR and GPC. The block copolymer PLA-b-PLL, combining the characteristics of an aliphatic polyester and poly(amino acids), could be of potential interest in a variety of medical applications, such as the fields of targeted drug delivery and gene delivery systems.     

Silkworm silk/poly(lactic acid) biocomposites: Dynamic mechanical, thermal and biodegradable properties

Silkworm silk/Poly(lactic acid) (silk/PLA) biocomposites with potential for environmental engineering applications were prepared by using melting compound methods. By means of Dynamic mechanical analysis (DMA), Differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA), Coefficient of thermal expansion test, Enzymatic degradation test and Scanning electron microscopy (SEM), the effect of silk fiber on the structural, thermal and dynamic mechanical properties and enzymatic degradation behavior of the PLA matrix was investigated. As silk fiber was incorporated into PLA matrix, the stiffness of the PLA matrix at higher temperature (70-160 °C) was remarkably enhanced and the dimension stability also was improved, but its thermal stability became poorer. Moreover, the presence of silk fibers also significantly enhanced the enzymatic degradation ability of the PLA matrix. The higher the silk fiber content, the more the weight loss.     

氨基酸-稳定同位素稀释质谱法用于合成肽段准确含量分析

建立了氨基酸同位素稀释液相色谱-串联质谱法准确测定合成肽段绝对含量的方法。实验中对合成肽段的纯度进行了表征,色谱纯度表征结果为99%以上,质谱纯度为90%以上。在肽段溶液中加入13C标记的氨基酸后进行酸溶液水解时间的优化,水解后的氨基酸直接经液相色谱分离和质谱检测,结果表明肽段中的被测氨基酸在150 ℃、6 mol/L HCl溶液水解4～6 h就可以达到水解平衡。每个肽段选择两个或两个以上的被测氨基酸,测得随机选择的5种合成肽段的绝对含量为62.07%～88.18%,测定结果的相对标准偏差小于8%,相对误差小于5%,均满足定量要求。除常用的被测氨基酸苯丙氨酸、缬氨酸、异亮氨酸外,还考察了选择赖氨酸和精氨酸作为被测氨基酸的可行性,实验结果表明增加精氨酸为被测氨基酸是可行的,从而进一步增加了方法的普适性。该方法的建立避免了色谱法定量时氨基酸衍生化处理带来的副反应影响及操作繁琐等问题,提高了肽段含量测定的准确度和精密度,为肽段含量的准确测定提供了一种新的方法。     

A Genetically Encoded Isonitrile Lysine for Orthogonal Bioorthogonal Labeling Schemes

Bioorthogonal click-reactions represent ideal means for labeling biomolecules selectively and specifically with suitable small synthetic dyes. Genetic code expansion (GCE) technology enables efficient site-selective installation of bioorthogonal handles onto proteins of interest (POIs). Incorporation of bioorthogonalized non-canonical amino acids is a minimally perturbing means of enabling the study of proteins in their native environment. The growing demand for the multiple modification of POIs has triggered the quest for developing orthogonal bioorthogonal reactions that allow simultaneous modification of biomolecules. The recently reported bioorthogonal [4 + 1] cycloaddition reaction of bulky tetrazines and sterically demanding isonitriles has prompted us to develop a non-canonical amino acid (ncAA) bearing a suitable isonitrile function. Herein we disclose the synthesis and genetic incorporation of this ncAA together with studies aiming at assessing the mutual orthogonality between its reaction with bulky tetrazines and the inverse electron demand Diels–Alder (IEDDA) reaction of bicyclononyne (BCN) and tetrazine. Results showed that the new ncAA, bulky-isonitrile-carbamate-lysine (BICK) is efficiently and specifically incorporated into proteins by genetic code expansion, and despite the slow [4 + 1] cycloaddition, enables the labeling of outer membrane receptors such as insulin receptor (IR) with a membrane-impermeable dye. Furthermore, double labeling of protein structures in live and fixed mammalian cells was achieved using the mutually orthogonal bioorthogonal IEDDA and [4 + 1] cycloaddition reaction pair, by introducing BICK through GCE and BCN through a HaloTag technique.     

产物可用电喷雾质谱检测的氨基酸/肽季铵化新方法

氨基酸和肽中氨基的化学修饰反应,如乙酰化反应和烷基化反应已被广泛用于蛋白组学研究中蛋白质的定量分析．氨基酸和肽的季铵化产物具有独特的优点,在电喷雾质谱中具有很好的离子化效率,可大大提高检测的灵敏度．文献[6～8]报道的氨基酸和肽的季铵化方法均使用高浓度的盐(如KHCO3),严重影响了质谱的检测结果,难以直接用于蛋白质组学研究．     

经济实用的Boc保护氨基酸键合氯甲基树脂的方法研究

在固相多肽合成中, 探索一种经济有效的Boc保护氨基酸键合氯甲基树脂的方法. 采用K₂CO₃/KI作为键合试剂, 一步合成产物, 反应条件为: Boc保护氨基酸2.5倍量, K₂CO₃ 2.5倍量, KI 0.01倍量, 氯甲基树脂1.0倍量, 普通DMF作反应溶剂, 70 ℃空气浴中旋转反应25 h. 考察了28种不同结构的氨基酸底物在此条件下与氯甲基树脂的键合收率, 大多数氨基酸都能得到几乎定量的酯化产率. 并选取了不同空间位阻的4种Boc保护氨基酸, 比较了KOH, Cs₂CO₃, TEA/KI, DCHA/KI, DIPA/KI, Cs₂CO₃/KI和K₂CO₃/KI等不同键合条件对收率的影响. 结果表明, 除Boc-Asn-OH外, K₂CO₃/KI条件与Cs₂CO₃/KI的效果大体相同, 但K₂CO₃/KI更为经济、可行.     

微波作用下大位阻氨基酸与H-Pro-CTC树脂的高效缩合

微波反应下, 运用新型固相肽合成反应器, 深入研究了五种大位阻氨基酸与H-Pro-CTC树脂(CTC树脂, 2-氯三苯甲基氯树脂)的缩合反应. 使用三次缩合的策略, 分别在DMF/NMP/THF (V∶V∶V＝1∶1∶1), NMP/DMSO/THF (V∶V∶V＝4∶1∶1), DMF/DMSO/THF (V∶V∶V＝4∶1∶1)混合溶剂中缩合一次, 每次缩合反应的最优条件为: 缩合试剂HBTU、氨基酸浓度7 mmol/L、微波辐射3 min、反应温度35 ℃、维持时间3 min, 与传统方法相比, 氨基酸的用量大大减少, 其过量倍数从5倍降低为2倍, 缩合反应速率提高了16倍以上. 五种大位阻氨基酸与H-Pro-CTC树脂的缩合率都提高到80%以上.     

A New Hybrid Model of Amino Acid Substitution for Protein Functional Classification

In recent years, methods of protein sequences analysis have been gradually evolved into two directions: One is based on the models of probability and statistics1-4; the other is based on the digital signal processing technologies 5-8. The latter mainly converts the protein character sequences into digital signals and uses some signal processing methods to analyze them, i.e., fast Fourier transform (FFT). However, it is still unsolved how to characterize the protein sequences accurately with …     

一种新型脱氧核糖核酸序列表征子及其应用于E.coli启动子对RNA转录启动强度的QSAM研究

从天然碱基的36种性质参数出发,通过主成分分析(PCA)技术处理得到了1个显著的主成分得分,并将该得分作为单个碱基的信息描述子———VBPV。进而使用VBPV对38个大肠杆菌(E.coli)启动子序列一级结构进行表征,并结合多元统计方法将表征参数与转录启动强度(PS)成功地建立了定量序列活性模型(QSAM),该模型拟合复相关系数Rcum与交叉检验复相关系数Qcum分别为0.97和0.95。     

一类全新阿片样二肽的设计合成及镇痛活性研究

阿片系统是疼痛研究的重要靶点, 阿片肽作为一类内源性的神经递质参与诸多生理调节尤其是在痛觉方面的调节, 被视为潜在的可以替代吗啡的深层次痛觉调节药物. 然而由于其固有的酶解稳定性差、镇痛作用不持久、难以透过血脑屏障等缺陷, 从而限制了其在临床方面的应用. 我们从阿片肽构效关系的角度出发, 设计并合成了4个新型二肽化合物, 在多种疼痛模型中显示, 中枢系统注射这类化合物能够表现出明显的镇痛活性, 外周系统注射发现这类化合物可以通过血脑屏障在中枢神经系统发挥有效的镇痛作用. 这一类二肽阿片化合物在多种实验模型中都表现出较好的药理学活性, 有可能发展为一类新型具有临床应用潜力的镇痛药物先导化合物.     

A Novel Protein Assay With an Azo Dye Using Rayleigh Light Scattering Technioque

ABSTRACT

The interaction of SPADNS [3-(4-sulfophenylazo)-4, 5-dihydroxy-2, 7-naphthalene disulfonic acid] with proteins in acidic solution was studied by spectrophotometric and Rayleigh light scattering (RLS) methods. SPADNS reacts rapidly with albumin at room temperature, and the intensity of the weak RLS of SPADNS was enhanced remarkably and quantitatively by this reaction.

Based on this observation, a novel RLS method for serum albumin determination was developed. The linear range is 0.125-14.9 μg/ml for BSA. The relative standard deviation (n=10) for 5.0 μg/ml BSA was 3.94%. The method was applied to the determination of proteins in human plasma, and the results were compared with the traditional proteins assay (CBB method). There is almost no interference from amino acids, metal ions and other coexistent substances. The reaction mechanism was also discussed.     

螯合金属离子亲和色谱法分离α-氨基酸和肽

以ＳｅｐｈａｄｅｘＧ１０为基质螯合二价铜离子的亲和色谱法分离α－氨基酸和肽，使之得以完全分离。对分离过程的原理进行了讨论。     

液相色谱-串联质谱法检测雄蜂蛹粉中50种抗生素残留

建立了液相色谱-串联质谱检测雄蜂蛹粉中50种抗生素残留（大环内酯类、喹诺酮类、磺胺类、四环素类、硝基咪唑类、林可霉素和氯霉素）的方法。样品经高氯酸溶液和醋酸铅溶液提取沉淀蛋白质，清液用磷酸氢二钾溶液调节pH值至8，经固相萃取净化后进行仪器分析。采用多反应监测正离子或负离子模式检测，可以一次完成对雄蜂蛹粉中50种目标化合物的定性和定量测定。50种抗生素的加标回收率为70.2%~118.3%，相对标准偏差（RSD）为1.8%~13.6%。该方法操作简便，灵敏度高，适用于雄蜂蛹粉中多种兽药残留的分析确证。     

液相色谱-串联质谱法测定水稻中生长素及其氨基酸结合物

建立了同时测定水稻中吲哚-3-丁酸(IBA)、吲哚-3-乙酸(IAA)及其7种氨基酸结合物的液相色谱-串联质谱( HPLC - MS/MS)检测方法.样品在4℃下于80％甲醇中浸提12 h后,经混合阴离子交换反相固相萃取(MAX)净化,以5 mmol/L的甲酸铵溶液和甲醇为流动相,在C18柱上进行液相色谱分离,电喷雾正...     

超高效液相色谱-高分辨质谱法测定中华绒螯蟹中游离氨基酸

游离氨基酸不仅是一类重要的营养物质,更与中华绒螯蟹独特的滋味和香味密切相关。对游离氨基酸含量进行测定,能为中华绒螯蟹产品的品质评价和风味研究提供有价值的信息。该工作通过优选提取溶剂、优化仪器测定参数,最终使用5%(v/v)高氯酸水溶液提取目标物,采用XDB-C₁₈色谱柱(100 mm×4.6 mm, 1.7μm),以0.1%(v/v)甲酸水溶液-乙腈为流动相进行梯度洗脱,在电喷雾正离子电离、选择离子扫描模式下进行检测,外标法定量,建立了超高效液相色谱-高分辨质谱(UHPLC-HRMS)测定中华绒螯蟹中17种游离氨基酸含量的方法。结果表明,17种氨基酸在10.0～200.0 mg/L范围内线性关系良好,相关系数(R²)≥0.999 0,仪器检出限为0.3 mg/L,仪器定量限为1.0 mg/L。在中华绒螯蟹可食部分中按三水平进行加标回收试验,各目标物的回收率在78.4%～105.3%之间。通过对仪器和方法精密度进行评估,发现17种氨基酸测定仪器重复性的RSD≤4.2%,方法重复性试验的RSD≤5.2%,再现性试验的RSD≤11.4%,精密度数据...