聚乙二醇二缩水甘油醚交联氨基载体LX-1000EA固定化脂肪酶 *

聚乙二醇二缩水甘油醚(PEGDGE)作为双功能环氧试剂,在实验中被用于交联氨基载体LX-1000EA共价固定化海洋脂肪酶,经过处理后的载体共价固定化脂肪酶具有良好的效果。实验经过单因素初筛和正交试验,得到最佳的交联及固定化条件为0.75%交联剂浓度、交联温度35℃、交联时间3h、载体量1.25g、pH9.0、固定化温度55℃、固定化时间1h。对LX-1000EA-PEGDGE固定化酶与游离酶、戊二醛(GA)交联LX-1000HA-GA的固定化酶进行酶学性质的比较,发现LX-1000EA- PEGDGE固定化酶较游离酶最适反应温度未改变,与LX-1000HA-GA相同的是最适反应pH都由7.0提高为8.0。在最适条件中所测LX-1000EA-PEGDGE酶活达到78.84U/g,固定化改变了游离酶的酸碱耐受性,热稳定性和操作稳定性较游离酶和LX-1000HA-GA固定化酶均有提高。LX-1000EA-PEGDGE的热稳定表现优异,在60℃孵育3h后保留90%酶活;使用5次后仍能残余50%酶活;保存30天酶活仍保留60%。首次使用新型双环氧交联剂PEGDGE交联有机氨基载体共价结合固定化脂肪酶,为更有效的固定化方法提供了技术支持,同时也发现交联剂对固定化酶的性质存在较大影响。     

DNA damage in the early primordial anther is closely correlated with stamen arrest in the female flower of cucumber (<Emphasis Type="Italic">Cucumis sativus</Emphasis> L.)

To investigate the regulatory mechanisms of sex expression in cucumber, morphological observations and biochemical analyses were carried out on inappropriate stamen development of female flowers of cucumber. It was found that developmental arrest of the inappropriate stamen mainly occurs at the anther primordium. This arrest is closely correlated with DNA damage, as detected by TUNEL assay, and might result from anther-specific DNase activation. It was also found that the DNA damage does not lead to cell degeneration, although chromatin condensation is observed in the anther primordia.Abbreviations DAPI 4,6-diamidine-2-phenylindole dihydrochloride - MTT 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide - PCD programmed cell death - TUNEL TdT-mediated dUTP nick-end labeling     

The mechanism of myoblast deformation in response to cyclic strain - A cytomechanical study

Mechanical strain is one of the important epigenetic factors that cause deformation and differentiation of skeletal muscles. This research was designed to investigate how myoblast deformation occurs after cyclic strain loading. Myoblasts were passaged three times and harvested; various cyclic strains (2.5kPa, 5kPa and 10kPa) were then loaded using a pulsatile mechanical system. The adaptive response of the myoblasts was observed at different time points (0.5h, 1h, 6h and 12h) post-loading. At the early stage of cyclic strain loading (<1h), almost no visible morphological changes were observed in the myoblasts. The actin cytoskeleton showed a disordered arrangement and a weak fluorescence expression; there was little expression of talin. At 6h and 12h post-loading, the myoblasts changed their orientation to parallel (in the 2.5kPa and 5kPa groups) or perpendicular (in the 10kPa group) to the direction of strain. Fluorescence expression of both the actin cytoskeleton and talin was significantly increased. The results suggest that cyclic strain has at least two ways to regulate adaptation of myoblasts: (1) by directly affecting actin cytoskeleton at an early stage post-loading to cause depolymerization; and (2) by later chemical signals transmitted from the extracellular side to intracellular side to initiate repolymerization.     

细叶黄芪叶肉原生质体发育早期细胞壁再生的研究

采用透射电镜术、电镜多糖细胞化学染色、细胞壁荧光染色以及香豆素抑制细胞壁再生等方法,对细叶黄芪（Ａｓｔｒａｇａｌｕｓｍ ｅｌｉｌｏｔｏｉｄｅｓ ｖａｒ．ｔｅｎｕｉｓ）叶肉原生质体细胞壁的再生及其化学特点进行了研究。结果表明,离体培养２４ 小时的原生质体表面产生一些突起小泡,有时可见少量纤维组分的形成。培养３ 天时这种纤维组分明显增多。至５ 天时可清楚看到再生壁是由纤维和颗粒构成。六亚甲四胺银染色证明它们都是由多糖组分组成的。另外,培养３６ 小时的原生质体有相互粘连的现象。电镜观察、荧光染色及香豆素处理的研究表明粘连与再生壁的形成有关。根据上述观察结果,对原生质体再生壁的结构及其化学性质等问题进行了讨论     

乳腺癌易感蛋白2的结构和功能

乳腺癌易感蛋白2是由乳腺癌易感基因2编码的一种在维持哺乳动物细胞染色体的稳定及DNA损伤生物应答中发挥重要作用的蛋白质。文章通过介绍近几年来对乳腺癌易感蛋白2的结构研究,阐述其在双链DNA损伤修复中的作用模型及其在肿瘤抑制中的功能。     

Photoaffinity labeling identifies the substrate-binding site of mammalian squalene epoxidase

Squalene epoxidase (SE) catalyzes the conversion of squalene to (3S)-2,3-oxidosqualene. Photolabeling and site-directed mutagenesis were performed on recombinant rat SE (rrSE) in order to identify the location of the substrate-binding site and the roles of key residues in catalysis. Truncated 50-kDa rrSE was purified and photoaffinity labeled by competitive SE inhibitor (Ki=18.4 microM), [(3)H]TNSA-Dza. An 8-kDa CNBr/BNPS-skatole peptide was purified and the first 24 amino acids were sequenced by Edman degradation. The sequence PASFLPPSSVNKRGVLLLGDAYNL corresponded to residues 388-411 of the full-length rat SE. Three nucleophilic residues (Lys-399, Arg-400, and Asp-407) were labeled by [(3)H]TNSA-Dza. Triple mutants were prepared in which bulky groups were used to replace the labeled charged residues. Purified mutant enzymes showed lower enzymatic activity and reduced photoaffinity labeling by [(3)H]TNSA-Dza. This constitutes the first evidence as to the identity of the substrate-binding site of SE.     

光动力疗法辅助治疗轻中度牙周炎的疗效观察

目的:探讨光动力疗法(PDT)辅助治疗轻中度牙周炎患者的临床疗效。方法:选取我院2016年1月-2017年8月收治的轻中度牙周炎患者46例为研究对象,共选取患牙276颗,随机分为观察组与对照组,每组138颗患牙,对照组予以龈下刮治术和根面平整术(SRP)治疗,观察组在对照组的基础上联合PDT治疗,比较治疗前、治疗后1个月、2个月、3个月观察两组患者的牙周袋探诊深度(PD)、探诊出血(BOP)阳性率、出血指数(BI)。结果:治疗后1个月、2个月、3个月,两组PD均随着时间的推移逐渐变浅(P0.05),且观察组治疗后各时间点均浅于对照组(P0.05);两组BOP阳性率均较治疗前降低,且观察组治疗后各时间均低于对照组(P0.05);两组BI随着时间的推移呈逐渐下降趋势(P0.05),且观察组治疗后各时间点BI均低于对照组(P0.05)。结论:PDT辅助治疗轻中度牙周炎患者的临床疗效较好,其能减小PD,降低BI和BOP阳性率。     

西双版纳人工雨林群落结构及其林下降雨侵蚀力特征

通过与本地典型的橡胶林和季节雨林进行对比,研究了在橡胶林基础上抚育、恢复而来的人工雨林群落结构及林下降雨侵蚀力特征.通过16a的抚育管理,人工雨林Shannon-Wiener多样性指数达到3.652,接近当地季节雨林的一般情况.对6a的降雨侵蚀力计算发现,人工雨林7月林内降雨侵蚀力达962.2 MJ mm hm-2 h-1 a-1,对旷地降雨侵蚀力的削减量是橡胶林的2.08倍.人工雨林初步重现了类似热带自然雨林的群落结构和叶面积指数特征,能够有效对削减降雨侵蚀力,这有利于林内水土保持和进一步的植被恢复.因此,人工雨林的抚育、恢复模式是热带退化山地地区植被恢复与重建的一条较为可行的途径.