Structural Basis for The Recognition of Deaminated Nucleobases by An Archaeal DNA Polymerase

With increasing temperature, nucleobases in DNA become increasingly damaged by hydrolysis of exocyclic amines. The most prominent damage includes the conversion of cytosine to uracil and adenine to hypoxanthine. These damages are mutagenic and put the integrity of the genome at risk if not repaired appropriately. Several archaea live at elevated temperatures and thus, are exposed to a higher risk of deamination. Earlier studies have shown that DNA polymerases of archaea have the property of sensing deaminated nucleobases in the DNA template and thereby stalling the DNA synthesis during DNA replication providing another layer of DNA damage recognition and repair. However, the structural basis of uracil and hypoxanthine sensing by archaeal B-family DNA polymerases is sparse. Here we report on three new crystal structures of the archaeal B-family DNA polymerase from Thermococcus kodakarensis (KOD) DNA polymerase in complex with primer and template strands that have extended single stranded DNA template 5’-overhangs. These overhangs contain either the canonical nucleobases as well as uracil or hypoxanthine, respectively, and provide unprecedented structural insights into their recognition by archaeal B-family DNA polymerases.     

D-核糖高产菌株的选育及其生产性试验

BacillussubtilisJSIM 10 18菌株是 1株产D 核糖的莽草酸营养缺陷型突变株 ,以此菌株为出发菌株 ,通过甲基磺酸乙酯和紫外线连续、间断诱变处理 ,获得了 1株次黄嘌呤、莽草酸双重缺陷型突变株No .2 71菌株。该突变株摇瓶发酵的D 核糖平均产量为 10 8 1g/L ,比亲株提高了 15 8g/L。在 30 0 0 0L发酵罐中 ,连续 5罐批 ,平均产D 核糖 96 4 g/L ,最高为 98g/L ,比亲株提高了 16 2 5 g/L。     

泰山虫草菌丝体与冬虫夏草有效成分的TLCS分析

以腺苷、尿苷、次黄嘌呤核苷、虫草素及次黄嘌呤为指标,测定泰山虫草菌丝体与天然冬虫夏草中相应成分的含量,探索泰山虫草代替天然冬虫夏草开发药物或保健食品的可能性。采用80%乙醇超声提取,在GF254硅胶板上点样后,以薄层色谱扫描法(TLCS)测定上述各种成分的含量。首次证明泰山虫草菌丝体核苷类及次黄嘌呤等有效成分含量明显高于冬虫夏草。其腺苷、尿苷、次黄嘌呤核苷、次黄嘌呤含量分别是冬虫夏草的8.25倍、3.76倍、11.8倍和1.55倍。2种虫草中有效成分的含量均表现为尿苷>次黄嘌呤核苷>腺苷>次黄嘌呤>虫草素。说明泰山虫草可以作为冬虫夏草代用品进行综合开发利用。TLCS法简捷快速,重现性、稳定性良好,能有效地对虫草中的有效成分进行定性定量分析。     

Antioxidative activities of bran extracts from twenty one pigmented rice cultivars

Ethanol–water (70:30, v/v) extracts from the bran of rice seeds from twenty one pigmented and one nonpigmented rice cultivars were evaluated for antioxidative activities using the following tests: inhibition of peroxidation of linoleic acid; inhibition of peroxidation of rabbit lipid erythrocyte membranes; reduction of potassium ferricyanide, and scavenging of superoxide anions and hydroxyl radicals. With some exceptions, extracts from the pigmented rice seeds had higher antioxidative activity than did the nonpigmented variety. The following pigmented cultivars had the highest antioxidative activities in all tests: Jumlalocal-1, Parnkhari 203, DZ78, LK1-3-6-12-1-1, and Elwee. A significant correlation was also noted between reducing power, inhibition of erythrocyte ghost membrane peroxidation, and superoxide anion and hydroxyl radical scavenging. The results suggest that: (a) ferricyanide reducing power might be a useful and simple index for large-scale evaluation of antioxidative potencies of natural products present in rice; (b) pigmented rice varieties with high antioxidative activities provide a source of antioxidants and a genetic resource to develop new health-promoting rice cultivars.     

Novel Measurement of Hypoxanthine in Fish Using Direct Measurement Probe and Chemiluminescence Flow Injection Analysis

Direct measurements of hypoxanthine (Hx) in fish flesh were carried out using a sardine and a grunt twice with the same fish, and the average of 10 successive measurements (from 120 sec to 480 sec after pressing the probe against fish tissue) was taken as the Hx concentration by direct measurement. Results with two nearby tissues of one sample were 42.9 ± 4.9 μM and 42.6 ± 2.6 μM for the sardine, and 639 ± 33 μM and 598 ± 29 μM for the grunt. For sardine, Hx results from this direct method did not agree well with perchloric acid extraction measurements, but they were much better for grunt.     

Quality Changes of Pond-raised Hybrid Striped Bass during Chillpack and Refrigerated Storage

Pond-raised hybrid striped bass were commercially processed into fillets with and without belly flap, packaged in oxygen permeable bags (Cryovac E^(tm)), and stored as chillpack samples (-2°C) and as refrigerated samples (2°C). Quality changes were determined over 21 days storage by microbiological, chemical, and sensory evaluations. Aerobic plate counts and hypoxanthine formation showed evidence of rapid deterioration of refrigerated samples after 8 days storage compared to 21 days for chillpack samples. A trained sensory panel found 21 day stored chillpack samples similar in flavor and aroma but of firmer texture than refrigerated samples stored 8 days. Panelists found no differences between trimmed and whole fillets. Hypoxanthine formation and aerobic plate counts appeared to be good indicators of quality deterioration, whereas thiobarbituric acid measurements were not.     

Nitrogenous constituents in the urine of cattle,sheep and goats

Ten samples of urine from dairy cows, five from sheep and four from goats were analysed to assess the distribution of urinary nitrogen (N) among various chemical constituents in order to gain a better understanding of the reactions undergone by urinary N in soil. Total N in the cow urine ranged from 6.8 to 21.6 g N litre^?1, of which an average of 69% was present as urea, 7.3% as allantoin, 5.8% as hippuric acid, 3.7% as creatinine, 2.5% as creatine, 1.3% as uric acid, 0.5% as xanthine plus hypoxanthine, 1.3% as free amino acid N and 2.8% as ammonia. In the sheep urine, total N ranged from 3.0 to 13.7 g litre^?1 of which an average of 83 % was present as urea; creatine accounted for 5.3% of the N; hippuric acid and allantoin both accounted for 4.3%, while each of the other constituents amounted to less than 1% of the total N. The goat urine was similar to the sheep urine but with a lower ratio of creatine to creatinine and a somewhat higher proportion (2.0 %) of the total N as amino acid.     

基于铜纳米簇模拟酶活性建立比色法测定鱼肉中的次黄嘌呤

基于铜纳米簇（copper nanoclusters,CuNCs）的过氧化氢（H2O2）模拟酶活性,建立鱼肉中次黄嘌呤（hypoxanthine,Hx）含量快速检测的比色分析方法。通过室温搅拌法得到半胱氨酸（cysteine,Cys）-CuNCs,利用透射电镜、光电子能谱、傅里叶变换红外光谱和荧光光谱,分别表征Cys-CuNCs的形貌、元素组成、表面官能团和发光特征。紫外-可见光谱实验表明,Cys-CuNCs能灵敏催化H2O2氧化3,3’,5,5’-四甲基联苯胺显色,实现对H2O2含量的比色测定。在此基础上,利用Hx在黄嘌呤氧化酶的作用下生成H2O2,建立了一种检测Hx的比色分析方法。当孵育温度30 ℃、孵育时间1 h时,Hx浓度在4～100 μmol/L范围内与吸光度呈良好的线性关系,检出限为1.2 μmol/L。将该方法应用于鱼肉中Hx含量的测定,并通过与总挥发性盐基氮建立相关性,实现对鱼肉新鲜度的判断。     

超高效液相色谱-串联质谱法测定鸡肉中肌苷及其关联物

建立一种利用超高效液相色谱-串联质谱法检测鸡肉中5’-腺苷酸（5’-adenosine monophosphate,AMP）、5’-肌苷酸（5’-inosine monophosphate,IMP）、肌苷（inosine,I）、次黄嘌呤（hypoxanthine,Hx）的方法,并进行方法学考察。结果表明：优化后的方法为样品中加入体积分数3%高氯酸-10%甲醇水溶液后添加匀浆均质子涡旋,离心,调节提取液pH值为5.0后用PEIME HLB柱净化,采用SB-Aq色谱柱（3.0 mm×100 mm,1.8 μm）,流动相为体积分数0.1%甲酸水溶液-乙腈,梯度洗脱,流速0.3 mL/min,正离子多反应监测模式测定,外标法定量;经方法学考察,4 种核苷类成分（AMP、IMP、I、Hx）线性关系良好,相关系数均大于0.996,加标回收率为79.63%～91.08%,相对标准偏差为1.0%～4.5%（n=6）。     

腺苷的合成新工艺研究

以次黄嘌呤为原料与三氯氧磷反应制得 6 氯嘌呤 ,收率为 90 .0 % ;6 氯嘌呤再与四乙酰核糖缩合、氨解制得腺苷 ,收率分别为 75 .0 %和 6 6 7%。三步反应的总收率为 45 %。实验验证 :缩合反应的最佳温度为 130～ 140℃ ,氨解反应最佳条件为 :用 0℃饱和氨甲醇溶液 ,加热至 10 0℃氨解 10h。产品经TLC、IR、1HNMR和MS确证