Human genetic deficits in glycan formation

Glycans are associated with most proteins found in secretions and on the surface of mammalian cells. Glycans of secreted glycoproteins affect many protein properties such as solubility, stability, protease sensitivity, and polarity, while glycans on cell surface glycoproteins are involved in various cellular functions including cell-cell and cell-matrix interactions during embryogenesis, immune reactions, and tumor development. Recent advances in human genomic research together with newly developed and sensitive methods for the analysis of glycan structures have elucidated the etiology of a growing number of human genetic diseases with aberrant glycan formation. Among these diseases, defects of protein N-glycosylation and O-mannosylation are reviewed here. The former is relatively common and the latter is rather uncommon. Both types of defects lead to severe abnormalities, which indicate the importance of glycosylation. Sequencing of the human genome is essentially complete and now glycobiology becomes an important area of postgenomic research. Glycobiology is expected to produce remarkable advances in the understanding and treatment of certain genetic diseases.     

The Potential Role of Polyphenols in Modulating Mitochondrial Bioenergetics within the Skeletal Muscle: A Systematic Review of Preclinical Models

Polyphenols are naturally derived compounds that are increasingly being explored for their various health benefits. In fact, foods that are rich in polyphenols have become an attractive source of nutrition and a potential therapeutic strategy to alleviate the untoward effects of metabolic disorders. The last decade has seen a rapid increase in studies reporting on the bioactive properties of polyphenols against metabolic complications, especially in preclinical models. Various experimental models involving cell cultures exposed to lipid overload and rodents on high fat diet have been used to investigate the ameliorative effects of various polyphenols against metabolic anomalies. Here, we systematically searched and included literature reporting on the impact of polyphenols against metabolic function, particularly through the modulation of mitochondrial bioenergetics within the skeletal muscle. This is of interest since the skeletal muscle is rich in mitochondria and remains one of the main sites of energy homeostasis. Notably, increased substrate availability is consistent with impaired mitochondrial function and enhanced oxidative stress in preclinical models of metabolic disease. This explains the general interest in exploring the antioxidant properties of polyphenols and their ability to improve mitochondrial function. The current review aimed at understanding how these compounds modulate mitochondrial bioenergetics to improve metabolic function in preclinical models on metabolic disease.     

Pt在SAPO-11分子筛上的分散性研究

采用H2-TPR、NH3-TPD、H2脉冲化学吸附和H2-O2化学滴定等方法对Pt/SAPO-11催化剂上金属分散进行了表征,并与该催化剂制备因子及其正构烷烃骨架异构化反应性能进行关联。实验表明,以与NH3配位的阳离子形式制备的催化剂,Pt的分散效果最好;用低浓度浸渍液、多次浸渍的方式制备的催化剂,Pt的分散度高;Mn2+、Sm3+、Zn2+等作助剂和Pd-Pt复合浸渍可提高Pt的分散度。调整分子筛的酸量使之与金属含量达到平衡时,催化剂活性和选择性最佳。     

基于易损性与冗余度分析的构件重要性评价方法

为合理评价构件在结构中的重要性,以构件材料的弹性模量为基本参数,并考虑构件刚度变化产生的影响,基于构件应变能对材料弹性模量的敏感性,建立了构件冗余度及其易损性评价指标,以衡量构件的脆弱性和冗余特性。在此基础上将构件的重要性指标定义为构件易损性系数与冗余度系数的比值,实现构件重要性的分类量化。结果表明,采用的构件重要性评价指标能正确反映构件在结构中的重要性,重要性系数高的构件为结构的高易损-低冗余构件,是结构的关键部位和薄弱环节所在,其失效后对结构整体性能的影响较大。加强高易损-低冗余关键构件对于提高结构的整体性能和抗连续倒塌的能力具有重要作用。     

d-Allulose Ameliorates Skeletal Muscle Insulin Resistance in High-Fat Diet-Fed Rats

Background: d-Allulose is a rare sugar with antiobesity and antidiabetic activities. However, its direct effect on insulin sensitivity and the underlying mechanism involved are unknown. Objective: This study aimed to investigate the effect of d-allulose on high-fat diet (HFD)-induced insulin resistance using the hyperinsulinemic–euglycemic (HE)-clamp method and intramuscular signaling analysis. Methods: Wistar rats were randomly divided into three dietary groups: chow diet, HFD with 5% cellulose (HFC), and HFD with 5% d-allulose (HFA). After four weeks of feeding, the insulin tolerance test (ITT), intraperitoneal glucose tolerance test (IPGTT), and HE-clamp study were performed. The levels of plasma leptin, adiponectin, and tumor necrosis factor (TNF)-α were measured using the enzyme-linked immunosorbent assay. We analyzed the levels of cell signaling pathway components in the skeletal muscle using Western blotting. Results: d-allulose alleviated the increase in HFD-induced body weight and visceral fat and reduced the area under the curve as per ITT and IPGTT. d-Allulose increased the glucose infusion rate in the two-step HE-clamp test. Consistently, the insulin-induced phosphorylation of serine 307 in the insulin receptor substrate-1 and Akt and expression of glucose transporter 4 (Glut-4) in the muscle were higher in the HFA group than HFC group. Furthermore, d-allulose decreased plasma TNF-α concentration and insulin-induced phosphorylation of stress-activated protein kinase/Jun N-terminal kinase in the muscle and inhibited adiponectin secretion in HFD-fed rats. Conclusions: d-allulose improved HFD-induced insulin resistance in Wistar rats. The reduction of the proinflammatory cytokine production, amelioration of adiponectin secretion, and increase in insulin signaling and Glut-4 expression in the muscle contributed to this effect.     

Nucleotides Induced Changes in Skeletal Muscle Myosin by DSC,TMDSC and EPR

Electron paramagnetic resonance (EPR, ST-EPR) and differential scanning calorimetry(DSC) were used in conventional and temperature modulated mode to study internal motions and energetics of myosin in skeletal muscle fibres in different states of the actomyosin ATPase cycle. Psoas muscle fibres from rabbit were spin-labelled with an isothiocyanate-based probe molecule at the reactive sulfhydryl site (Cys-707) of the catalytic domain of myosin. In the presence of nucleotides (ATP, ADP, AMP⋅PNP) and ATP or ADP plus orthovanadate, the conventional EPR spectra showed changes in the ordering of the probe molecules in fibres. In MgADP state a new distribution appeared; ATP plus orthovanadate increased the orientational disorder of myosin heads, a random population of spin labels was superimposed on the ADP-like spectrum. In the complex DSC pattern, higher transition referred to the head region of myosin. The enthalpy of the thermal unfolding depended on the nucleotides, the conversion from a strongly attached state of myosin to actin to a weakly binding state was accompanied with an increase of the transition temperature which was due to the change of the affinity of nucleotide binding to myosin. This was more pronounced in TMDSC mode, indicating that the strong-binding state and rigor state differ energetically from each other. The different transition temperatures indicated alterations in the internal microstructure of myosin head region The monoton decreasing TMDSC heat capacities show that C _p of biological samples should not be temperature independent. This revised version was published online in August 2006 with corrections to the Cover Date.     

促进组织生长的聚合物骨架工程材料

对组织工程中影响细胞生长规律的两个主要因素：材料的表面性质和表面形貌进行了讨论，指出材料的生物相容性应同时包括表面相容性和结构相容性。对于可促进组织生长的聚合物骨架材料的结构设计，必须同时兼顾材料的表面工程和结构２工程，二者必不可少且不可分割。     

过渡金属硫簇的几种簇骼转化反应

报道了过渡金属硫簇化合物的几种簇骼转化反应，即三核链状簇的转化；双核配合物的组合；Ｍｏ２Ｆｅ７Ｓ８和Ｍｏ２Ｆｅ６Ｓ８两种双立方烷的关联；Ｆｅ４Ｓ４立方烷簇向篮状簇的转化；簇降解以及簇骼原子置换反应等。探讨了配体及氧化还原条件对簇骼转化反应的影响。     

Analysis of Acidic Properties of Zeolitic and Non-Zeolitic Solid Acid Catalysts Using Temperature-Programmed Desorption of Ammonia

A method of ammonia temperature-programmed desorption (TPD) for analysis of acidic property of a solid was improved by introduction of a water vapor treatment method and development of a theory for calculation of ammonia adsorption heat from the TPD profile. The improved method was applied to various solid acid catalysts to establish relationships between the acidic properties and catalytic performances for various acid-catalyzed reactions. Here, examples of the applications to some important acid catalysts are reviewed. The exact analysis of acidic property of Y zeolite and its change by such modifications as steaming and ethylenediaminetetraacetic acid (EDTA) treatment gave a new interpretation on the generation of alkane (paraffin) cracking activity on an ultra stable Y (USY) zeolite. The surface density and strength of acid sites on WO₃/ZrO₂ and SO₄ ^2–/ZrO₂ catalysts were determined, and their relations with catalytic activities for Friedel–Crafts type alkylation and skeletal isomerization of alkane were found.