蛋白质表面模块划分及其在结合位点预测中的应用

蛋白质-蛋白质复合物的结合位点预测是计算分子生物学的一个难题. 本文对蛋白质-蛋白质复合物数据集Benchmark 3.0 中的双链蛋白质复合物进行了研究, 计算了单体的残基溶剂可接近表面积和残基间的接触面积, 并据此提出了蛋白质表面模块划分方法. 发现模块的溶剂可接近表面积与其内部接触面积的乘积(PSAIA)值能够提供结合位点的信息. 在78 个双链蛋白质复合物中, 有74 个体系其受体或配体上具有最大或次大PSAIA值的模块是界面模块. 将该方法获得的结合位点信息应用在CAPRI竞赛Target 39 的复合物结构预测中取得了较好的结果. 本文提出的基于模块的蛋白质结合位点预测方法不同于以残基为基础且仅考虑表面残基的传统预测方法, 为蛋白质-蛋白质复合物结合位点预测提供了新思路.     

Analysis of Influential Factors of Konjac Glucomannan（KGM） Molecular Structure on Its Activity

Biological activity of konjac glucomannan is closely related to its structure,in particular to its high-level structure.Researches on the activity mechanism of konjac glucomannan are significant for revealing the mysteries of participation in life activity.In this paper,analysis of the effects of konjac glucomannan configuration and various factors on its structure and activity was conducted,mechanism of biological activity of konjac glucomannan was explored,and the hot research topic of konjac glucomannan was given.     

Theoretical Study on the Reaction of Thymine with Iodomehane in the Water Phase

The reaction mechanisms of carcinogenic methylating agent iodomethane (MeI) with keto and enol tautomers of thymine (K- and E-thymine) were studied by using the B3LYP/6-311+G (d, p) method in water phase. The solvent effects were examined using the polarizable continuum model (PCM). Specifically, PCM single-point calculations at the same level of theory were performed in acetone and CCl4 that represent a range in nonpolarity. The calculated results show that the reaction of K-thymine with MeI is a two-step mechanism, whereas that of E-thymine is a one-step mechanism. Our calculations reveal that K-thymine is appreciably more stable than the enol form in the water phase or in the two solvents. The K- and E-form reaction barriers are 135.6 and 222.1 kJ/mol, respectively in water phase. These findings indicate that the reactions mentioned above could not occur efficiently in biological media in the absence of catalyst. Our conclusions are in agreement with the previous studies on the reactions of guanine with methyl chloride and methyl bromide.     

融合注意力和Inception模块的脑白质病变端到端分割

针对目前磁共振脑影像上脑白质高信号区域的自动分割存在分割精度较低和细小病灶易漏识等问题,提出一种融合注意力和Inception的U-Net分割模型。在U-Net的编码阶段加入Inception模块以增加网络宽度,使其具有多尺度特征的提取能力,并加入注意力模块以增强网络对分割目标的关注度,两者的加入和融合可以有效提升网络的特征提取和表达能力。同时,在解码阶段的每一个卷积层上增加残差连接,可以提高网络的优化速度。此外,针对样本不均衡易导致分割结果中假阴性过多的问题,采用具有均衡调节能力的Tversky损失函数优化网络训练。实验结果表明,所提方法能够较好地分割脑白质的高信号区域,特别是小病灶区,且各项分割指标优于多个对比方法。     

改进狼群算法求解多目标柔性作业车间调度问题

针对传统智能优化算法求解多目标柔性作业车间调度时存在算法后期收敛速度慢、易陷入局部最优的问题,本文提出一种将量子粒子群算法中的三大重要性能参数和狼群算法融合的混合优化算法.首先,构建以最大完工时间、机器总负荷和瓶颈机器负荷为优化目标的多目标数学模型;其次,采用高斯分布的概率密度函数产生随机变量进行种群初始化操作,以提高...     

A New Cooperation Mechanism of Kinesin Motors when Extracting Membrane Tube

Membrane tubes are important functional elements for riving cells. Experiments have found that membrane tubes can be extracted from giant lipid vesicles by groups of kinesin. How these motors cooperate in extracting the membrane tube is a very important issue but still unclear so far. In this paper, we propose a cooperation mechanism called two-track-dumbbell model, in which kinesin is regarded as a dumbbell with an end （tail domain） tethered on the fluid-like membrane and the other end （head domain） stepping on the microtubule. Taking account of the elasticity of kinesin molecule and the excluded volume effect of both the head domain and the tail domain of kinesin, which are not considered in previous models, we simulate the growth process of the membrane tube pulled by kinesin motors. Our results indicate that in the case of strong or moderate exclusion of motor tails, the average number of motors pulling the tube can be as high as 9 and thus motors moving along a single microtubule protofilament can generate enough force to extract membrane tubes from vesicles. This result is different from previous studies and may be tested by future experiments.     

探秘氧化锌纳米结构

在过去二十多年里,人们对氧化锌纳米结构进行了大量研究,揭示了其丰富的形貌、生长特性和物理性质。在不使用催化剂的条件下,直接用锌粉和氧气合成、生长氧化锌纳米单晶可能得到其生长机制的本征信息。图中所示是在未加催     

低温下单根ZnO纳米带电学性质的研究

用化学气相沉积法在硅衬底上合成了宽1 μm左右、长数十微米的ZnO纳米带. 采用微栅模板法得到单根ZnO纳米带半导体器件, 由I-V特性曲线测得室温下ZnO纳米带电阻约3 MΩ, 电阻率约0.4 Ω·cm. 研究了在20–280 K温度范围内单根ZnO纳米带电阻随温度的变化. 结果表明: 在不同温度区间内电阻随温度变化趋势明显不同, 存在两种不同的输运机制. 在130–280 K较高的温度范围内, 单根ZnO纳米带电子输运机制符合热激活输运机制, 随着温度继续降低(< 130 K), 近邻跳跃传导为主导输运机制. 关键词： ZnO 纳米带 低温 输运机制     

两时间尺度下非光滑广义蔡氏电路系统的簇发振荡机理

通过引入周期变化的电流源并选择适当参数, 使得周期激励频率与系统固有频率之间存在量级差距, 建立了两时间尺度即快慢耦合非光滑广义蔡氏电路模型. 基于相应的广义自治系统, 考察了其不同区域中的平衡态及其稳定性, 得到了不同分岔行为及其相应的临界条件. 同时, 利用广义Clarke导数得到的广义Jacobian矩阵, 探讨了系统轨迹穿越非光滑分界面时的各种非常规分岔模式, 进而结合广义相图, 深入分析了Fold/Fold周期簇发振荡以及Fold/Hopf周期簇 发振荡两种典型的周期簇发行为及其相应的分岔机制. 关键词： 非光滑 广义蔡氏电路 两时间尺度 分岔机制     

Three dimensional simulations of penetrative convection in a porous medium with internal heat sources

The problem of penetrative convection in a fluid saturated porous medium heated internally is analysed. The linear instability theory and nonlinear energy theory are derived and then tested using three dimensions simulation.Critical Rayleigh numbers are obtained numerically for the case of a uniform heat source in a layer with two fixed surfaces. The validity of both the linear instability and global nonlinear energy stability thresholds are tested using a three dimensional simulation. Our results show that the linear threshold accurately predicts the onset of instability in the basic steady state. However, the required time to arrive at the basic steady state increases significantly as the Rayleigh number tends to the linear threshold.