MyristoylCoA:protein N-Myristoyltransferase: Probing Host-Guest Interactions Using Synthetic Substrates

MyristoylCoA:protein N-myristoyl transferase (NMT) catalyzes the cotranslational covalent attachment of myristate (C14:0) to the ammo-terminal glycine residues of a variety of biologically important proteins. An extensive survey of myristic acid analogs has previously allowed us to infer the conformational constraints imposed upon the fatty acid when bound to the enzyme's acylCoA binding site. A series of myristic acid analogs has now been synthesized and studied in an in vitro assay to probe further the conformation of NMT's bound ligand and to assess the importance of the distance between the carboxyl and the proposed bend in the fatty acid.     

醇水混合溶剂中沉淀无机晶体的研究

文章研究了醇水混合溶剂中无机物沉淀结晶的一些规律。研究结果表明,通过选择合适的实验条件,混合溶剂可以有效调控无机晶体的结晶行为,为控制无机晶体的晶型、形貌、尺寸等提供了可借鉴方法。     

Geometric Frustration in Molecular Crystals

Unlike Lego bricks that perfectly assemble next to one another, solid assemblies of organic compounds often include some inevitable misfit between constituents, giving rise to geometric frustration. In order to fit into the assembly the molecular building blocks must distort, at some finite energetic cost. In cases where this distortion at the ground state is uniform across all the units in the assembly, the associated geometric frustration is said to be locally resolved. Such locally resolved frustration carries little implications on the morphology and response properties of the assembled structure. However, in many cases, for small enough assemblies there are non-local compromises that are more energetically favorable. These conformations are associated with non-uniform distortions and highly cooperative response between the molecular constituents. The cooperative nature of frustrated assemblies may result in growth arrest, tendency to form filaments, exotic response properties and large morphological variations during the growth of the assembly. Almost a century ago German mineralogist Ferdinand Bernauer discovered that a large fraction of small organic compounds could form twisted molecular crystals. These are straight and narrow needle-like structures with mesoscopic pitch, a crystalographically impossible structure. Recent revived interest in twisted molecular crystals discovered even more compounds that form these exotic assemblies and led to their study by modern means. Electron microscopy revealed straight faceted structures with sharp diffraction peaks in selected area electron diffraction, much like regular crystals. Moreover, the pitch of the molecular crystals varied with size, with thicker crystals exhibiting less twist. In this work we review twisted molecular crystals as frustrated assemblies. In this approach twist emerges from the preferred morphology at the constituent scale, and gets attenuated with size by the incompatibility of twist and large-scale crystalline order. We discuss two distinct mechanisms that produce twisted molecular crystals, and provide a prediction for the twist decay as a function of the crystals’ spatial dimensions.     

Experimental Aspects of Colloidal Interactions in Mixed Systems of Liposome and Inorganic Nanoparticle and Their Applications

In the past few years, growing attention has been devoted to the study of the interactions taking place in mixed systems of phospholipid membranes (for instance in the form of vesicles) and hard nanoparticles (NPs). In this context liposomes (vesicles) may serve as versatile carriers or as a model system for biological membranes. Research on these systems has led to the observation of novel hybrid structures whose morphology strongly depends on the charge, composition and size of the interacting colloidal species as well as on the nature (pH, ionic strength) of their dispersing medium. A central role is played by the phase behaviour of phospholipid bilayers which have a tremendous influence on the liposome properties. Another central aspect is the incorporation of nanoparticles into vesicles, which is intimately linked to the conditions required for transporting a nanoparticle through a membrane. Herein, we review recent progress made on the investigations of the interactions in liposome/nanoparticle systems focusing on the particularly interesting structures that are formed in these hybrid systems as well as their potential applications.     

On Molecular Sieve-Water Interactions

Introduction

Adsorption of water vapor on a molecular sieve is probably one of the most common examples of industrial thermal swing adsorption processes. It is therefore not surprising that this has attracted significant attention in the past, and the subject has been studied extensively both experimentally and theoretically. Some of the major contributions include the early work of Carter (l), Nutter and Burnet (2), and Carter and Barrett (3) among others. These systems were recently reviewed by Basmadjian (4) and Ruthven (5). Despite these attempts, there are a number of features which make the interactions between a molecular sieve and water unique in that such interactions are not generally seen on any other adsorbents.

     

When Supramolecular Chemistry Meets Chemical Biology: New Strategies to Target Proteins through Host-Guest Interactions

Supramolecular chemistry for targeting proteins is of great interest for the development of novel approaches to recognize, isolate and control proteins. Taking advantage of chemical biology approaches, such as genetic-code expansion and enzyme-mediated ligation, guest recognition elements can be built into proteins of interest, allowing supramolecular control of protein function and regulation. In this viewpoint article, we will discuss the methods, applications, limitations, and future perspectives of supramolecular chemistry for targeting proteins in a site-specific manner.     

SBA-15介孔分子筛及其主-客体复合材料研究的某些进展

对分子筛的发展历程、SBA-15介孔分子筛的合成方法、近年来以SBA-15介孔分子筛作主体合成主-客体复合材料的研究情况、SBA-15分子筛及其复合材料的应用进行了综述,并对SBA-15介孔分子筛在未来的发展进行了展望.     

共聚高分子体系的分子热力学模型

以共聚硬球链流体的分子热力学模型为基础,通过引入链节间方阱位能相互作用的贡献。建立了实际共聚高分子系统的分子热力学模型,对纯共聚高分子ＰＶＴ的关系结果,平均相对误差为０．２２％－０．８０％。     

Molecular Interactions in Polysaccharide Gelation

The gel structures formed by naturally occurring polysaccharides, either in vivo (in, for example, plant tissue) or in vitro after extraction and purification, are normally crosslinked by extended intermolecular ‘junction zones’ of conformationally ordered chains. Formation and disruption of these ordered structures under biologically and industrially relevant conditions of extensive hydration may be monitored and characterised by a variety of physical techniques, in conjunction with x-ray analysis at atomic resolution in the condensed phase by fibre diffraction. Interconnecting regions of residual disorder, necessary for solubilisation of the gel network, may be introduced by structural irregularities or block character in the primary sequence.     

非共价分子印迹体系的快速筛选方法

分子印迹是一项制备对特定目标分子具有高度特异性和选择性分子识别材料的新兴仿生技术,但分子印迹体系的筛选繁琐而耗时。综述了目前常用的 4种快速筛选方法。     

New Approaches to Solvent-Mediated Molecular Interactions

Recently developed integral equation methods for the evaluation of intermolecular and intramolecular interactions in a polar solvent medium are discussed and representative applications are presented. Examples include solvent modification of interionic interactions between atomic or molecular ions in water and liquid environment induced shifts in conformational equilibria for both non-polar and polar flexible molecules in water. Emphasis is placed on the features of these phenomena which can be traced specifically to the molecularity of the solvent and hence cannot be adequately reproduced by a simple continuum dielectric solvent representation.     

Structuring of Macroporous Silicon for Applications as Photonic Crystals

Uniformity and high refractive index contrast make macroporous silicon an ideal two-dimensional photonic crystal, that can be tailored over a wide range of frequencies. For optical transmission measurements the porous silicon has to be structured further. Light has to be coupled in perpendicular to the pore axis and to traverse a well defined number of pore layers. For this purpose a lateral structuring technique has been developed that allows to remove the porous silicon with a precision of less than one pore lattice constant. Bars of macroporous silicon which are 100 m high, 2–200 m wide and several mm long have been prepared. These bars have been aligned with designed defect structures like linear or bent waveguides in the porous silicon. The achieved samples are well suited to investigate the optical properties of these defects with light traveling perpendicular to the pore axis.     

Mixed Mode I—Mode III Fracture in Ceramic Single Crystals

A recently reported method has been used to propagate stable mixed mode I-mode III cracks in thin slices of single-crystal α-quartz (low quartz, SiO₂) and single-crystal rutile (TiO₂). A bond-counting technique has been developed and used to isolate planes of weakness in the crystalline structures of both crystals. Good correlation has been obtained with observed crack planes. Mode III component (K_III) versus crack velocity (v) relations for specified mode I contributions have thus been determined for m {10 1 0} fracture in basal (0001) slabs and for {a+c} fracture in m {10 1 0} slabs of α-quartz and also for (110) fracture in basal (001) and (101) fracture in (010) slabs of rutile.     

Assembling Molecular Guidance Systems for Heterogeneous Enantioselective Catalysis

Creating successful heterogeneous enantioselective catalysts remains an important goal for the chemicals and pharmaceuticals industries, with considerable attention being focused on chirally modified metals as promising candidates. Here, recent surface science results are reviewed, which throw a new and intriguing light on these modified metal surfaces, highlighting new phenomena such as complex adsorption phases, two-dimensional organization, and the surprising creation of extended chiral surfaces. This molecular level information provides an important and fresh input into future design strategies.     

Probing Water Diffusion Inside Crystals of AlPO-5 by PFG NMR and IRM for Heat Storage Applications

Diffusion of water in the aluminophosphates AlPO-5 is studied using a combination of pulsed field gradient NMR and IR microimaging. The concentration profiles measured by the latter allowed to visualize the process of water sorption and propagation into the crystals of AlPO-5. The self-diffusion coefficients obtained by NMR were one order of magnitude higher values compared to corrected ones from the IR microimaging study. The concentration profiles allowed to visualize the process of water sorption and propagation into the crystals of AlPO-5. The obtained results are compared with experimental and simulation data for the water/AlPO-5 system for the literature and discussed in the context of its potential use for heat storage applications.