Natural nano-machines

In the first part of this article, we read about Alice’s guided tour through the cellular microfactory. In the second part, I introduce the methods of studying the materials and mechanisms of the molecular machines through dialogues. The three participants in this discussion are Alice, her elder brother Alex and her father Albert. The style of presentation here is adapted from Galileo’s Dialogue Concerning the Two Chief World Systems. Albert, a professor of biophysics, emphasizes the crucial differences between the mechanisms of the natural nano-machines and those of their macroscopic counterparts. He also points out some practical applications of this interdisciplinary research in biomedical science and nano-technology. Debashish Chowdhury is a professor of Physics at IIT Kanpur. He is a theoretical physicist and the areas of his research interest are statistical and biological physics. He plays with toy models using mathematical formulae and simulates nature with computers.     

真核细胞内蛋白质的定向转运

真核细胞内的蛋白质合成以后要被运送至不同部位行使不同的功能。根据转运机制的不同,分为膜泡运输、跨膜转运以及选择性的门控转运。无论通过哪一种方式转运,存在于蛋白质中起信号作用的氨基酸序列是必不可少的。     

离子迁移数的探讨

从定义出发,通过公式推导、简单图解法、物料衡算法和例题分析,对离子迁移数的概念进行了剖析,并得到了相应等式．通过学习能够熟练掌握离子迁移数本质内容,提高学生学习物理化学的兴趣．     

细胞膜Na+-K+主动输运过程的热力学分析

研究分析了Na^ -K^ 在跨膜主动输运过程中，细胞能量(由ATP分解提供)在各阶段的耗散情况．并且把ATP酶视为一个子系统，探讨了其在一个循环中发生的生物物理过程的规律性，对于深入了解细胞生命活动的内在机制提供了一种有益的研究方法。     

Determination of Diffusion Coefficient and Analysis of Diffusion Factors of Cr(Ⅵ) Ion in Clay Soil

Some laboratory diffusion tests were conducted with diffusion device to determine the diffusion coefficient of Cr(Ⅵ) ion passing through Dalian red clay samples. The concentrations of Cr(Ⅵ) at different places of the samples were then measured spectrophotometrically after a standing time of 1 000 d. A one-dimensional solute transport equation was used to simulate the transport of Cr(Ⅵ) through clay samples. Back-calculation of diffusion coefficient of Cr(Ⅵ) was made with finite difference method. Parametric...     

Determination of Diffusion Coefficient and Analysis of Diffusion Factors of Cr（Ⅵ） Ion in Clay Soil

Some laboratory diffusion tests were conducted with diffusion device to determine the diffusion coefficient of Cr(Ⅵ) ion passing through Dalian red clay samples. The concentrations of Cr(Ⅵ) at different places of the samples were then measured spectrophotometrically after a standing time of 1 000 d. A one-dimensional solute transport equation was used to simulate the transport of Cr(Ⅵ) through clay samples. Back-calculation of diffusion coefficient of Cr(Ⅵ) was made with finite difference method. Parametric analysis was conducted to simulate variations in soil dry density, temperature, pH and standing time. The results show that the method used in this paper is simple and effective. The diffusion coefficient of Cr(Ⅵ) in Dalian red clay varies from 1.50×10-7 cm2/s to 2.08×10-7 cm2/s. After 1 000 d diffusion, the concentration of the source solution drops down to 1.27 mg/L from 62.5 mg/L, and the diffusion distance is only 3.5 cm. Under the assumption that diffusion coefficient is constant, the diffusion effect becomes more obvious with lower density, lower temperature, higher pH value, and much more time.     

一种计算蛋白质等电点和中性离子最大分布系数的简便方法

从多元弱酸分步电离的角度出发,从理论上推导一种计算蛋白质等电点和中性离子的最大分布系数的方法.即设蛋白质中性离子左右各存在Ⅱ种由相同游离氨基酸残基电离出的正负离子,且Km、km+1分别为该两种游离氨基酸残基的电离常数,当满足u≥umin=2/pKm+1-pKm[lg(√KmKm+1/Kn-u+Kn+u+1/√KmKm+1)+2]时,蛋白质的等电点为pI=1/2(pKm+pKm+1),中性离子的最大分布系数为1/1+2u∑i=1(Km+1/Km)i/2.文中将公式应用于胰岛素和胰高血糖素两种蛋白质体系,计算结果与实验值相符且较文献方法简单方便.     

天然"豆皮"速溶饮料的研究

本文提出了一种天然"豆皮"速溶饮料生产新的技术与工艺方法.产品的理化指标及微生物学指标符合GB/T标准,含有18种氨基酸,其中9种为必需氨基酸.将其放入100℃沸水中冲泡1～3min,搅溶,即得清凉可口、保持原有豆皮的色、香、味等天然品质的"豆皮"速溶饮料.     

Overexpression of the steroidogenic acute regulatory protein increases the expression of ATP-binding cassette transporters in microvascular endothelial cells (bEnd.3)

Objective:To determine the effect of steroidogenic acute regulatory protein(StAR) overexpression on the levels of adenosine triphosphate(ATP)-binding cassette transporter A1(ABCA1) and ATP-binding cassette transporter G1(ABCG1) in an endothelial cell line(bEnd.3).Methods:The StAR gene was induced in bEnd.3 cells with adenovirus infection.The infection efficiency was detected by fluorescence activated cell sorter(FACS) and fluorescence microscopy.The expressions of StAR gene and protein levels were detected ...