Reconstructing a Flavodoxin Oxidoreductase with Early Amino Acids

Primitive proteins are proposed to have utilized organic cofactors more frequently than transition metals in redox reactions. Thus, an experimental validation on whether a protein constituted solely by early amino acids and an organic cofactor can perform electron transfer activity is an urgent challenge. In this paper, by substituting “late amino acids (C, F, M, T, W, and Y)” with “early amino acids (A, L, and V)” in a flavodoxin, we constructed a flavodoxin mutant and evaluated its characteristic properties. The major results showed that: (1) The flavodoxin mutant has structural characteristics similar to wild-type protein; (2) Although the semiquinone and hydroquinone flavodoxin mutants possess lower stability than the corresponding form of wild-type flavodoxin, the redox potential of double electron reduction E_m,7 (fld) reached −360 mV, indicating that the flavodoxin mutant constituted solely by early amino acids can exert effective electron transfer activity.     

Mixed protein-templated luminescent metal clusters (Au and Pt) for H2O2 sensing

A simple and cost-effective method to synthesize the luminescent noble metal clusters (Au and Pt) in chicken egg white aqueous solution at room temperature is reported. The red-emitting Au cluster is used as fluorescent probe for sensitive detection of H₂O₂.     

Chromatographic characterisation of aptamer-modified poly(EDMA-co-GMA) monolithic disk format for protein binding and separation

The introduction of aptameric ligands onto disk-monolithic adsorbent, representing a unique strategy for convective isolation of target molecules with high specificity and selectivity, is investigated for the first time. Experimental results showed that the disk monolith possessed a good permeability of 1.67 ± 0.05 × 10^–14 m² (RSD = 3.2%). The aptameric ligand density for the aptamer-modified disk monolith was 480 pmol/uL. Chromatographic analysis of the aptamer disk-monolith efficiency showed an optimum linear velocity of 126 cm/min (≈0.25 mL/min) at room temperatures 25 ± 2°C. The theoretical number of plates corresponding to the optimum linear velocity was 128.2 with an height equivalent to the theoretical plate of 0.022 mm. The disk aptamer-immobilised monolithic system demonstrated good selectivity and isolation of thrombin from non-targets.     

A Method for Systematic Assessment of Intrinsically Disordered Protein Regions by NMR

Intrinsically disordered proteins (IDPs) that lack stable conformations and are highly flexible have attracted the attention of biologists. Therefore, the development of a systematic method to identify polypeptide regions that are unstructured in solution is important. We have designed an “indirect/reflected” detection system for evaluating the physicochemical properties of IDPs using nuclear magnetic resonance (NMR). This approach employs a “chimeric membrane protein”-based method using the thermostable membrane protein PH0471. This protein contains two domains, a transmembrane helical region and a C-terminal OB (oligonucleotide/oligosaccharide binding)-fold domain (named NfeDC domain), connected by a flexible linker. NMR signals of the OB-fold domain of detergent-solubilized PH0471 are observed because of the flexibility of the linker region. In this study, the linker region was substituted with target IDPs. Fifty-three candidates were selected using the prediction tool POODLE and 35 expression vectors were constructed. Subsequently, we obtained ¹⁵N-labeled chimeric PH0471 proteins with 25 IDPs as linkers. The NMR spectra allowed us to classify IDPs into three categories: flexible, moderately flexible, and inflexible. The inflexible IDPs contain membrane-associating or aggregation-prone sequences. This is the first attempt to use an indirect/reflected NMR method to evaluate IDPs and can verify the predictions derived from our computational tools.     

以绿色木霉Trichodermaviride NUA-051及产朊假丝酵母Candida utilis发酵酸解玉米秸秆生产单细胞蛋白的艺研究

以蛋白质得率为目标,综合考虑绿色木霉(Trichodermaviride NUA-051)与产朊假丝酵母(Candida utilis)2.281的共生特性及营养竞争,通过木霉发酵产物还原糖对菌体生长抑制的实验研究及发酵条件实验,确立了以酸解玉米秸秆为原料生产单细胞蛋白的发酵工艺酸解玉米秸秆150g/L,木霉发酵40h接种酵母2%,(NH4)2SO4 25.0g/L,KH2PO4 6g/L、MgSO4·7H2O 0.4g/L,通风量为4.5L/L·min为,搅拌转速为600r/min,pH5～6,温度35℃.木霉发酵时间40h,酵母发酵时间24h,发酵总周期64h.     

改性大豆分离蛋白产品功能性及机理的研究

利用氮气和谷氨酰胺转胺酶(MTG)对大豆分离蛋白(SPI)进行复合改性.复合改性SPI的吸水性、保水性和吸油性分别比对照提高了121%、222%和150%;溶解性比对照降低了36%.经MTG改性后SPI可在分子间生成共价键,形成相对分子量较大的聚合物.复合改性可在MTG改性的基础上进一步增加SPI分子间的交联程度.     

发酵豆制品潜在风险因子分析

采集了59份重庆生产酱油、豆豉、腐乳和豆瓣酱4大类发酵豆制品,检测其理化指标和可能存在的6种风险因子,包括蛋白质降解物挥发性盐基氮、硫化氢和生物胺、防腐剂苯甲酸和丙酸及微生物代谢毒素黄曲霉毒素。结果表明,各类样品的pH值及总酸含量均在正常范围;腐乳及包装酱油样品所含氨基酸态氮含量均满足国家标准;各类生物胺普遍存在于发酵豆制品中,不同类型的样品中所含生物胺的种类和含量不同,主要含有酪胺和腐胺。腐乳中生物胺总量最高;挥发性盐基氮的含量较高,可能对样品安全性有影响;硫化氢含量较少,暂不影响食品的可食性;总黄曲霉毒素的含量均未超过国家限量标准,安全性良好。苯甲酸和丙酸普遍存在于各类发酵豆制品中,个别样品中苯甲酸和丙酸含量远高于国家的限量标准,问题较为突出。有必要追踪发酵豆制品加工及贮藏过程中风险因子的变化及产生规律,提出有效的质量安全控制措施。     

Adaptation of the ToxRTool to Assess the Reliability of Toxicology Studies Conducted with Genetically Modified Crops and Implications for Future Safety Testing

To determine the reliability of food safety studies carried out in rodents with genetically modified (GM) crops, a Food Safety Study Reliability Tool (FSSRTool) was adapted from the European Centre for the Validation of Alternative Methods’ (ECVAM) ToxRTool. Reliability was defined as the inherent quality of the study with regard to use of standardized testing methodology, full documentation of experimental procedures and results, and the plausibility of the findings. Codex guidelines for GM crop safety evaluations indicate toxicology studies are not needed when comparability of the GM crop to its conventional counterpart has been demonstrated. This guidance notwithstanding, animal feeding studies have routinely been conducted with GM crops, but their conclusions on safety are not always consistent. To accurately evaluate potential risks from GM crops, risk assessors need clearly interpretable results from reliable studies. The development of the FSSRTool, which provides the user with a means of assessing the reliability of a toxicology study to inform risk assessment, is discussed. Its application to the body of literature on GM crop food safety studies demonstrates that reliable studies report no toxicologically relevant differences between rodents fed GM crops or their non-GM comparators.     

乳清蛋白菊粉糖基化复合物的褐变特性与抗氧化活性

以褐变程度及抗氧化活性为检测指标,研究湿热反应条件对乳清蛋白菊粉糖基化复合物的褐变特性与抗氧化活性的影响。研究结果表明:反应物浓度越大,反应温度越高,乳清蛋白菊粉糖基化产物的褐变强度越大,抗氧化活性越强;起始反应pH值越大,乳清蛋白菊粉糖基化产物的褐变强度及还原能力越强,而其DPPH.清除能力呈现先升高后降低的趋势。当反应物浓度为6%,温度为100℃,起始反应pH值为9时,所获得的乳清蛋白糖基化产物抗氧化活性较强。