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1.
付里叶变换红外光谱法研究水在稳定多肽构象中的作用   总被引:1,自引:0,他引:1  
在0—100%相对湿度(RH)范围内用竹里叶变换红外光谱研究了水合对聚赖氨酸溴化氢结合物构象的影响。随相对湿度RH增加,水合分为:无规卷曲、β-折叠和α-螺旋三个稳定的阶段.多肽的水合行为远比报导的复杂,在三个阶段中都不是纯单一结构组分,在任何一个RH下都存在3-4个吸收组分。在RH>44%以上β特征吸收发生复杂变化,表明β-结构的类型可能发生变化。实验表明,水是肽链柔性的增塑剂,运动性和构象的催化剂。  相似文献   

2.
付里叶变换红外光谱定量法研究表明,在0~100%相对湿度(RH)范围内,聚赖氨酸溴化氢结合物(PLK-HBr)干膜的水合原则上分为无规卷曲、β-折叠和α-螺旋三个构象稳定阶段,其水合行为远较文献报导的复杂。在任一水合度下都不是纯单一结构,其红外谱均由多个吸收组分组成,而且,β-折叠的类型还可能发生变化。  相似文献   

3.
用荧光染色法研究了不同温度(10~30℃)和湿度(51~100%RH)组合条件下飞虱虫疠 霉 Pandora delphacis分生孢子的存活率。在无放回抽样观察中,孢子弹射后第24 h的存活 率在51%、74%、85%、90%、95%和100%RH与不同温度的组合中分别为42~81%、69~89%、70~ 95%、 67~100%、 76~100%和 56~100%。存放4个月后,不同温度下的孢子存活率在 51%、 74%、 85%和 90%RH下分别为 55~74%、 52~87%、 38~73%和 1~65%。而在≥95% RH下孢子存活率 24h 后锐减,至第7 d几乎全部失活。以上结果表明,弹射后的飞虱虫疠霉孢子在头24 h的存活 易受低湿影响,但存活下来的孢子能继续在低湿下存活较久;饱和或接近饱和的高湿度最不 利孢子长久存活。  相似文献   

4.
用本室制备的兔抗羊促肾上腺皮质激素释放激素(CRH)多克隆抗体和 ̄(125)I标记的Tyr°-rCRH建立了CRH放射免疫测定法。并用该方法测定了人胎盘组织和大鼠脑及胸腺组织CRH含量。所得抗体与rCRH的亲合常数Ka=5.3×10 ̄9L/mol,与促肾上腺皮质激素、血管紧张素I、β-内啡肽、生长激素释放因子、血管活性肠肽、胆囊收缩素、加压素等18种肽没有交叉反应。 ̄(125)I-rCRH的比放射性为4163kBq/μg。建成的CRH放射免疫测定法取代比率为2.29,灵敏度为40pg,ED_(50)约为650pg,百分精密度和百分准确度分别为3.84%和10.36%。用该法所测人胎盘和大鼠组织CRH含量的结果表明,分娩胎盘组织CRH含量远高于妊娠6─7周者,约相当于后者的15倍;大鼠组织CRH含量以下丘脑最高,垂体次之,然后依次是海马、胸腺和大脑皮质;且下丘脑和垂体的CRH含量雄鼠明显高于雌鼠。  相似文献   

5.
通过荧光光谱、紫外光谱、傅里叶红外光谱(FTIR)和远紫外圆二色光谱(Far-UV CD)对重金属Hg2+作用下木瓜蛋白酶的结构变化进行了定性定量的表征,探索Hg2+对木瓜蛋白酶变性的抑制机理。结果表明:Hg2+是木瓜蛋白酶的强抑制剂,10-4mol/L的HgCl2可使木瓜蛋白酶丧失90%的活性;随着金属Hg2+浓度的增加,蛋白质所处的微环境和二级结构发生了明显的改变,(α螺旋+β折叠)结构总量减少,无规则卷曲含量增多,酶的二级结构由规则有序转向无序。  相似文献   

6.
用分子定向进化技术,在酶活力和热稳定性双重选择压力下,筛选到了一体Keat/KM是天然酶47倍的进化酶。用FT-IR方法,测定了α-天门冬氨酰二须酶及其进化酶的酰胺I带图普,定量估算了天然酶和进化酶的各种二级结构含量。天然酶中,β折叠结构含量为28.5%,α螺旋结构含量为33%,这与园二色谱测量α螺旋结构为33%的结果有很好的一致,剩余的残基形成不同类型的转角和无规结构,其总含量为38.5%。在进化酶中,β折叠结构含量为26.8%,α螺旋结构含量为315,其它结构为不同类型的转角和无规结构,含量为42.2%。  相似文献   

7.
商品果胶酶中endo—PG的分离纯化及其部分性质研究   总被引:3,自引:0,他引:3  
以A.niger来源的果胶酶为材料,经过CM-Sephadex C-50及Sephadex G-100两步骤分离化得到电泳均一的endo-PG1及endo-PG2其亚基分子量分别为35kD及37kD,含糖量为11.22%及8.3%,最大此吸收峰分别在274nm及269nm处,氨基酸组成分析结果表明Gly含量较高,Met含量较低,不含Cys,并且酸性氨基酸含量高于碱性氨基酸,圆二色谱结果表明二级结构  相似文献   

8.
以A.niger来源的果胶酶为材料,经过CM-SephadexC-50及SephadexG-100两步骤分离纯化得到电泳均一的endo-PG1及endo-PG2,其亚基分子量分别为35kD及37kD,含糖量为11.22%及8.3%,最大紫外吸收峰分别在274nm及269nm处,氨基酸组成分析结果表明Gly含量较高,Met含量较低,不含Cys,并且酸性氨基酸含量高于碱性氨基酸,圆二色谱结果表明二级结构主要为α螺旋和β折叠,其中endo-PG1含α螺旋45.1%,β折叠24.9%;endo-PG2含α螺旋39.6%,β折叠36.5%。  相似文献   

9.
固有无序蛋白质(intrinsically disordered proteins,IDPs)是天然条件下自身不能折叠为明确唯一的空间结构,却具有生物学功能的一类新发现的蛋白质.这类蛋白质的发现是对传统的"结构-功能"关系认识模式的挑战.本文首先总结了无序蛋白质的实验鉴定手段、预测方法、数据库;并介绍了无序蛋白质结构(包括一级结构、二级结构、结构域无序性及变构效应)和功能特征;然后重点总结了无序蛋白质在进化角度研究的进展,包括无序区域产生的进化机制、进化速率,蛋白无序性的进化在蛋白质功能进化及生物学复杂性增加等方面的重要作用;最后展望了无序蛋白质在医药方面的应用前景.本文对于深入认识无序蛋白质的形成机制、结构和功能特征及其潜在的临床应用前景具有重要意义.  相似文献   

10.
首次尝试了将显微傅里叶变换红外光谱术应用于研究电融合后细胞膜蛋白质二级结构的变化,发现脉冲电场作用于细胞具有穿透效应,施加电脉冲后,整个细胞的蛋白质体系能量增加,表明电泳冲对蛋白的二结构影响很大;同时,还发现用唾液酸苷酶和蛋白酶Pronase分析处理巨噬细胞膜表面后,膜上蛋白质二级结构无序化程度增加,用酶适度处理的细胞将更易发生电融合。  相似文献   

11.
温、湿度对亚洲玉米螟成虫繁殖力及寿命的影响   总被引:10,自引:0,他引:10  
温度和湿度的变化对亚洲玉米螟0strinia furnacalis(Guenee)成虫的交配和产卵及寿命都具有极显著的影响。在16℃~32℃和RH20%~100%的温湿范围中,亚洲玉米螟成虫繁殖力在20℃~28℃恒温和RH70%~100%的温湿组合中较大,其中在24℃恒温和28℃~20℃变温与RH90%~100%的组合中为最大,在32℃和RH20%的组合中为最小。单雌抱卵量、产卵量和产出卵率及交配次数均与温度呈抛物线曲线关系,与湿度呈正相关。温、湿度对成虫繁殖力具有极显著的交互作用。成虫寿命与温湿度密切相关,温度越高,成虫寿命越短;而湿度越高,成虫寿命越长。但雄蛾比雌蛾较耐低湿,在16℃~24℃下雄蛾寿命比雌蛾较长。此外,雄蛾较强的交配能力可促进卵的发育和产出。以上结果对玉米螟种群动态消长的分析和预测预报提供了参考依据。  相似文献   

12.
Anhydrobiotic organisms accumulate late embryogenesis abundant (LEA) proteins, a family of intrinsically disordered proteins (IDPs) reported to improve cellular tolerance to water stress. Here we show that AfrLEA6, a Group 6 LEA protein only recently discovered in animals, protects lactate dehydrogenase (LDH), citrate synthase (CS) and phosphofructokinase (PFK) against damage during desiccation. In some cases, protection is enhanced by trehalose, a naturally-occurring protective solute. An open question is whether gain of secondary structure by LEA proteins during drying is a prerequisite for this stabilizing function. We used incremental drying (equilibration to a series of relative humidities, RH) to test the ability of AfrLEA2, a Group 3 LEA protein, to protect desiccation-sensitive PFK. AfrLEA2 was chosen due to its exceptional ability to protect PFK. In parallel, circular dichroism (CD) spectra were obtained for AfrLEA2 across the identical range of relative water contents. Protection of PFK by AfrLEA2, above that observed with trehalose and BSA, coincides with simultaneous gain of α-helix in AfrLEA2. At 100% RH, the CD spectrum for AfrLEA2 is typical of random coil, while at decreasing RH, the spectrum shows higher ellipticity at 191 nm and minima at 208 and 220 nm, diagnostic of α-helix. This study provides experimental evidence linking the gain of α-helix with stabilization of a target protein across a graded series of hydration states. Mechanistically, it is intriguing that certain other functions of these IDPs, like preventing aggregation of target proteins, can occur in fully hydrated cells and apparently do not require gain of α-helix.  相似文献   

13.
Intrinsically disordered proteins (IDPs) refer to those proteins without fixed three-dimensional structures under physiological conditions. Although experiments suggest that the conformations of IDPs can vary from random coils, semi-compact globules, to compact globules with different contents of secondary structures, computational efforts to separate IDPs into different states are not yet successful. Recently, we developed a neural-network-based disorder prediction technique SPINE-D that was ranked as one of the top performing techniques for disorder prediction in the biannual meeting of critical assessment of structure prediction techniques (CASP 9, 2010). Here, we further analyze the results from SPINE-D prediction by defining a semi-disordered state that has about 50 % predicted probability to be disordered or ordered. This semi-disordered state is partially collapsed with intermediate levels of predicted solvent accessibility and secondary structure content. The relative difference in compositions between semi-disordered and fully disordered regions is highly correlated with amyloid aggregation propensity (a correlation coefficient of 0.86 if excluding four charged residues and proline, 0.73 if not). In addition, we observed that some semi-disordered regions participate in induced folding, and others play key roles in protein aggregation. More specifically, a semi-disordered region is amyloidogenic in fully unstructured proteins (such as alpha-synuclein and Sup35) but prone to local unfolding that exposes the hydrophobic core to aggregation in structured globular proteins (such as SOD1 and lysozyme). A transition from full disorder to semi-disorder at about 30–40 Qs is observed in the poly-Q (poly-glutamine) tract of huntingtin. The accuracy of using semi-disorder to predict binding-induced folding and aggregation is compared with several methods trained for the purpose. These results indicate the usefulness of three-state classification (order, semi-disorder, and full-disorder) in distinguishing nonfolding from induced-folding and aggregation-resistant from aggregation-prone IDPs and in locating weakly stable, locally unfolding, and potentially aggregation regions in structured proteins. A comparison with five representative disorder-prediction methods showed that SPINE-D is the only method with a clear separation of semi-disorder from ordered and fully disordered states.  相似文献   

14.
Some simple lipid-water systems have been studied by x-ray scattering techniques, as a function of lipid concentration and temperature. Several liquid-crystalline phases have been found, and their structure has been determined: only one of these is lamellar. In all these phases the hydrocarbon part of the lipid molecules has a disordered, liquid-like structure. One biological phospholipid, a human brain extract, has been studied by the same technique, and two liquid-crystalline phases have been found: a lamellar phase, built up by an ordered sequence of lipid and water planar sheets, and a hexagonal phase, which is a hexagonal array of circular cylinders, each cylinder being a thin water channel covered by the hydrophilic groups of the lipid molecules, the hydrocarbon chains filling the gap between the cylinders. The interpretation of the electron microscope observations of the structure of lipoprotein membranes is discussed, and some possible biological implications are suggested.  相似文献   

15.
Unoriented films of calf thymus NaDNA with either 3.0 or 5.0 NaCl per base pair were prepared by dehydrating unstressed gels. These films were studied by Raman and ir spectroscopy. The 5.0 samples showed very strong vibrational modes characteristic of the B conformation at relative humidities (RH) as low as 30%, indicating that those samples were entirely in the B conformation. The 3.0 samples showed weaker features: some of the DNA in these samples were in the B conformation at 80% RH while the DNA is essentially in a disordered phase at 30% RH. © 1997 John Wiley & Sons, Inc.  相似文献   

16.
Short and long disordered regions of proteins have different preference for different amino acid residues. Different methods often have to be trained to predict them separately. In this study, we developed a single neural-network-based technique called SPINE-D that makes a three-state prediction first (ordered residues and disordered residues in short and long disordered regions) and reduces it into a two-state prediction afterwards. SPINE-D was tested on various sets composed of different combinations of Disprot annotated proteins and proteins directly from the PDB annotated for disorder by missing coordinates in X-ray determined structures. While disorder annotations are different according to Disprot and X-ray approaches, SPINE-D's prediction accuracy and ability to predict disorder are relatively independent of how the method was trained and what type of annotation was employed but strongly depend on the balance in the relative populations of ordered and disordered residues in short and long disordered regions in the test set. With greater than 85% overall specificity for detecting residues in both short and long disordered regions, the residues in long disordered regions are easier to predict at 81% sensitivity in a balanced test dataset with 56.5% ordered residues but more challenging (at 65% sensitivity) in a test dataset with 90% ordered residues. Compared to eleven other methods, SPINE-D yields the highest area under the curve (AUC), the highest Mathews correlation coefficient for residue-based prediction, and the lowest mean square error in predicting disorder contents of proteins for an independent test set with 329 proteins. In particular, SPINE-D is comparable to a meta predictor in predicting disordered residues in long disordered regions and superior in short disordered regions. SPINE-D participated in CASP 9 blind prediction and is one of the top servers according to the official ranking. In addition, SPINE-D was examined for prediction of functional molecular recognition motifs in several case studies.  相似文献   

17.
河蚌培养组织的几种生化成分分析   总被引:1,自引:0,他引:1  
本文分析测定了三角帆蚌,褶纹冠蚌和背角无齿蚌外套膜培养组织及其培养液中的氨基酸,牛磺酸及钙含量。在珍蛛中含量较高的丙的氨酸和甘氨酸分别增加541%和91%。三种蚌在培养中牛磺酸含量增加5.78%到3倍,培养组织的钙含量增加1倍左右。同时测定了培养组织的碱性磷酸酶活性,培养组织与河蚌外套膜具有相近的比活及相对酶活。结果表明,河蚌外套膜在离体培养条件下,也具有分泌珍珠质的能力。  相似文献   

18.
Abstract

Short and long disordered regions of proteins have different preference for different amino acid residues. Different methods often have to be trained to predict them separately. In this study, we developed a single neural-network-based technique called SPINE-D that makes a three-state prediction first (ordered residues and disordered residues in short and long disordered regions) and reduces it into a two-state prediction afterwards. SPINE-D was tested on various sets composed of different combinations of Disprot annotated proteins and proteins directly from the PDB annotated for disorder by missing coordinates in X-ray determined structures. While disorder annotations are different according to Disprot and X-ray approaches, SPINE-D's prediction accuracy and ability to predict disorder are relatively independent of how the method was trained and what type of annotation was employed but strongly depend on the balance in the relative populations of ordered and disordered residues in short and long disordered regions in the test set. With greater than 85% overall specificity for detecting residues in both short and long disordered regions, the residues in long disordered regions are easier to predict at 81% sensitivity in a balanced test dataset with 56.5% ordered residues but more challenging (at 65% sensitivity) in a test dataset with 90% ordered residues. Compared to eleven other methods, SPINE-D yields the highest area under the curve (AUC), the highest Mathews correlation coefficient for residue-based prediction, and the lowest mean square error in predicting disorder contents of proteins for an independent test set with 329 proteins. In particular, SPINE-D is comparable to a meta predictor in predicting disordered residues in long disordered regions and superior in short disordered regions. SPINE-D participated in CASP 9 blind prediction and is one of the top servers according to the official ranking. In addition, SPINE-D was examined for prediction of functional molecular recognition motifs in several case studies. The server and databases are available at http://sparks.informatics.iupui.edu/.  相似文献   

19.
Basic components of the water balance were determined in A. reflexus unfed second instar nymphs kept at 30 degrees C and different relative humidities in darkness. At 2.5% and 32.5% RH, A. reflexus survived for 170+/-60 and 246+/-71 days, respectively. At 56%, 75.5% and 96.5% RH, the experiment was terminated after 168 days without any mortality. The initial water content of hydrated A. reflexus kept at 85% RH was 70.3+/-1.8% while the water content was close to 50% in ticks dehydrated at /=56% suggesting that A. reflexus increased its oxidative metabolism under dehydrating conditions and thus delayed lethal dehydration. Interestingly, the dry mass of dead ticks was almost identical irrespective of whether the ticks had previously been kept at 2.5% and 32.5% RH, i.e. irrespective of their different survival periods. This raises the question whether the ticks had died by dehydration or by exhaustion of energy reserves.  相似文献   

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