Magnetic order in the Shastry-Sutherland model

We investigate the influence of energetic disorder, viscous damping and an external field on the electron transfer (ET) in DNA. The double helix structure of the λ-form of DNA is modeled by a steric oscillator network. In the context of the base-pair picture two different kinds of modes representing twist motions of the base pairs and H-bond distortions are coupled to the electron amplitude. Through the nonlinear interaction between the electronic and the vibrational degrees of freedom localized stationary states in the form of standing electron-vibron breathers are produced which we derive with a stationary map method. We show that in the presence of additional energetic disorder the degree of localization of such breathers is enhanced. It is demonstrated how an applied electric field initiates the long-range coherent motion of breathers along the bases of a DNA strand. These moving electron-vibron breathers, absorbing energy from the applied field, sustain energetic losses due to the viscous friction caused by the aqueous solvent as well as the impact of a moderate amount of energetic disorder. Moreover, it is illustrated that with the choice of the amplitude and frequency of the external field, the breather can be steered to a desired lattice position achieving control of the ET. Received 5 July 2002 Published online 29 November 2002     

Hydration of nucleic acid components in dependence on nucleotide composition and relative humidity: a Monte Carlo simulation

What role does the nucleotide composition play in the process of formation of hydrated environment of nucleic acids? Can one estimate the hydration of nucleic acids on the level of their components? In order to resolve these questions we have completed an extensive computer simulation of the hydration of nucleic acids components - deoxynucleoside monophosphates distinguished by nucleotide composition. The energetic characteristics of systems containing deoxynucleoside monophosphates and water clusters of various dimensions are received. Our results demonstrate that deoxynucleoside monophosphates containing guanine and/or cytosine residues hydrated more strongly because of formation of more hydrogen bonds with water molecules in small water clusters, i.e. at low values of relative humidity. With increasing of number of water molecules in a water cluster the energetic preference of deoxynucleoside monophosphates containing guanine and/or cytosine residues decreases, and for water clusters corresponding to a state of a dilute aqueous solution the hydration of all types of deoxynucleoside monophosphates does not differ in a great degree. Deoxynucleoside monophosphates containing guanine and/or cytosine residues cause the greater destruction of the water structure compensated by the greater interaction with the nearest water molecules for all levels of relative humidity. Received 25 December 2001 and Received in final form 22 March 2002 Published online 13 September 2002     

Solute effects on the helix-coil transition

We discuss the effects of the solvent composition on the helix-coil transition of a polypeptide chain. We use a simple model to demonstrate that improving the hydrogen-bonding ability of the solvent can make the transition less cooperative, without affecting the transition temperature. This effect is very different from other solvent effects which primarily influence the melting transition rather than the cooperativity. Received 10 December 2001 and Received in final form 22 March 2002     

联用技术应用于生物分子中金属和类金属的形态分析

本文依据最近有关联用技术应用于生物样品中痕量金属和类金属形态分析的报道,扼要介绍高效液相色谱（HPLC）和毛细管电泳（CE）与电感耦合等离子质谱（ICP－MS）和电喷雾离子化质谱（ESI－MS）联用技术在砷、硒和镉等元素的形态分析中的应用。体积排阻色谱（SEC）与ICP－MS在线联用最常用的初步筛选未知试样中大分子化合物的方法。但由于SEC的分辨率差,需要应用另一种色谱法,如离子交换色谱法（IEC）或反相色谱法（RP－HPLC）分离以保证分离信号的纯度。在无标准可利用的情况下,电喷雾串联质谱（ES－MS／MS）是用以表征化合物的最佳手段。毛细管区带电泳（CZE）与ICP－MS联用是形态分析的有用工具。分析中需要注意的问题是避免沾污和防止在分离过程中蛋白质的分解。目前,由于缺少标准和参考物质,联用技术主要应用于寻找新的金属物 种,而并非测定已知化合物。需要解决的难题是检测的信号是否属于某一特定的化合物以及该化合物的表征。     

表面分子印迹材料的制备及在生物分子分离分析中的应用

表面分子印迹技术是一种新型的分子印迹技术,其解决了传统印迹方法得到的印迹聚合物模板结合位点少、洗脱困难、色谱性能和机械性能差等问题。表面分子印迹聚合物(SMIPs)以其稳定性好、特异性高及实用性强的特点,近年来在生物分子分离分析中的应用引起人们的关注。本文介绍了SMIPs的制备方法,比较了不同方法的优缺点,并对其在生物大分子、生物小分子及微生物分子分离分析中的应用进行了综述。     

One-dimensional and two-dimensional nanomaterials for the detection of multiple biomolecules

By utilizing nanomaterials including one-dimensional materials (1DMs) and two-dimensional materials (2DMs), the recent development for the determination of multiple biomolecules has been focused.     

Cation binding to biomolecules

SCF ab initio computations are carried out on the binding of alkali and alkaline-earth cations to the phosphate monoanion. The effect of the binding on the conformational properties of the phosphodiester linkage and of the polar head of phospholipids is investigated. The results indicate that following the nature of the cation and the site of its binding, the interaction may have a profound influence on the conformation of the ligand. The consequences of this situation on the use of lanthanide probes in NMR studies are considered.     

Parameters optimization for biological molecules patterning using 248-nm ultrafast lasers

Laser-induced forward transfer has been used for the deposition of photoactive biotin in micron-scale patterns. The process uses a 500 fs pulsed KrF laser beam to transfer small amounts of a liquid solution target as micron-size droplets to a substrate placed parallel and in close proximity to it. The biomolecules remain active after the transfer; this is demonstrated through fluorescence assays. In addition to the laser parameters, those regarding the target composition and the receiving surface for the miniaturization of the transferred patterns have been studied and optimized. Droplets as small as 5 μm have been obtained by reducing the target thickness and transfer energy; by increasing the percentage of glycerol added in the biomolecules solution and by using hydrophobic surfaces as receiving substrates. The influence of the glycerol addition and the hydrophobicity of the receiving surfaces on the activity of the transferred biomolecules have also been studied.     

Packing nanomechanics of viral genomes

We investigate the osmotic equilibrium between a bulk polyethylene glycol (PEG) solution and DNA tightly packed in a spherical capsid. We base our analysis on the equations of thermodynamic equilibrium in terms of osmotic pressure. The equality between external osmotic pressure of PEG and osmotic pressure of tightly packed DNA gives us the DNA encapsidation curves. In this way we directly connect the wealth of existing osmotic pressure data for DNA in the bulk with the DNA encapsidation curves within small viral capsids. Specific calculations are made for a monovalent salt, Na(+) -DNA and a divalent salt, Mn(2+) -DNA that have quite different DNA encapsidation behaviors. The main conclusion of our work is that bending energy of DNA is of minor importance regarding the encapsidated DNA length, but has a non-negligible influence on the density distribution of DNA within the capsid.