Synthesis and properties of 8-CN-flavin nucleotide analogs and studies with flavoproteins

A high potential analog of riboflavin with a cyano function at the 8-position was synthesized by employing novel reaction conditions, starting from 8-amino-riboflavin. This was converted to the FAD level with FAD synthetase. The reduced 8-CN-riboflavin, unlike normal reduced flavin, has a distinctive absorption spectrum with two distinctive peaks in the near ultraviolet region. The oxidation-reduction potential of the new flavin was determined to be -50 mV, approximately 160 mV more positive than that of normal riboflavin. The 8-CN-riboflavin and 8-CN-FMN were found to be photoreactive and need to be protected from exposure to light. However such complications were not encountered with protein-bound flavins. The apoproteins of flavodoxin and Old Yellow Enzyme (OYE) were reconstituted with the 8-CN-FMN and apoDAAO was reconstituted with 8-CN-FAD. Spectral properties of the enzyme-bound neutral and anionic semiquinones were determined from these reconstituted proteins. In the case of 8-CN-FMN-OYE I, it was shown that the comproportionation reaction of a mixture of reduced and oxidized enzyme bound flavin is very rapid, compared with the same reaction with native protein, resulting in approximately 100% thermodynamically stable anionic semiquinone. In the case of 8-CN-OYE I, it was shown that the rate of reduction of the enzyme bound flavin by NADPH is approximately 40 times faster, and the rate of reoxidation of reduced enzyme bound flavin by oxygen is an order of magnitude slower than with the normal FMN enzyme. This is in accord with the high oxidation-reduction potential of the flavin, which thermodynamically stabilizes the reduced enzyme.     

Enhanced Na+/H+ exchange in Cushing's syndrome reflects functional hypermineralocorticoidism

BACKGROUND: Patients with Cushing's syndrome exhibit a bimodal distribution of maximal rates of the erythrocyte amiloride-sensitive Na+/H+ exchange (NHE). Enhanced erythrocyte NHE has recently been found in patients with primary aldosteronism. OBJECTIVE: To test the hypothesis that occult hypermineralocorticoidism in a subset of patients with Cushing's syndrome is responsible for the greater than normal NHE. METHODS: NHE was measured as maximal initial rate (Vmax) of amiloride-inhibited efflux of H+ into an alkaline Na+-containing medium, for 47 patients with hypercortisolism (20 with pituitary adenomas, 18 with adrenal adenomas, and nine with ectopic production of adrenocorticotropin). Clinical appearance, blood pressure levels, plasma aldosterone and deoxycorticosterone levels, serum electrolytes, and urine (tetrahydrocortisol plus 5-alpha-tetrahydrocortisol) : tetrahydrocortisone ratios were assessed for all patients. Twenty patients (10 with greater than normal NHE and 10 with low-to-normal NHE) were randomly selected from 47 patients with hypercortisolism, and treated with 200 mg/day spironolactone for 7 days. NHE in these patients was assessed before starting the treatment and 2 days after its cessation. RESULTS: Greater than normal NHE (Vmax) was associated with peripheral edema, high diastolic blood pressure, hypokalemia, and high urine (tetrahydrocortisol plus 5-alpha-tetrahydrocortisol) : tetrahydrocortisone ratios. The enhanced NHE was rapidly normalized by treatment with spironolactone. CONCLUSION: Erythrocyte NHE in patients with hypercortisolism and functional hypermineralocorticoidism is greater than normal due to incomplete peripheral conversion of cortisol (which binds to mineralocorticoid receptors) into metabolically inactive cortisone.     

新型坐标测量机结构设计及数学模型

文章阐述了新型平行双关节坐标测量机的优点,介绍了其机械结构设计和电机控制系统,建立了数学模型,为进一步进行误差补偿提供了理论基础。     

基于激光散射原理的表面粗糙度测量方法研究

文章基于Beckmann散射模型,提出一种表面粗糙度的在线测量方法。以半导体激光器为光源构成远心光路,通过线阵CCD记录粗糙物体表面的散射光场。计算机分析处理得到表面粗糙度特征值Sn,在较大的范围内表面粗糙度Ra和Sn有很好的对应关系。该测量方法结构简单、精度高、速度快,可以对不同加工方法的工件表面粗糙度实现非接触实时检测,在工件的在线检测方面有很好的发展前景。     

鲜湿面保鲜的研究与探讨

研究了几种天然防腐保鲜剂:乳酸链球菌素、溶菌霉等在延长鲜湿面保质期上的效果,并根据多种保鲜剂及辅助剂的互补增效作用,研究出了一种非常高效的复合天然食品保鲜剂(TKB06)。它可以大大延缓鲜湿面的微生物腐败变质,使鲜湿面保质期达到12月以上。     

基于LEON3的中央控制器设计及EDAC功能实现

针对目前空间机器人中央控制器运行速度较低、实时控制性弱等缺点,设计了基于LEON3处理器核的中央控制器,用做空间机器人控制的初步研究。同时,为了解决太空环境中电子控制系统中存储器易出现单粒子翻转效应(SEU)的问题,设计了一种基于Hsiao码的EDAC电路,以实现"纠一检二"(SEC-DED)的基本功能。使用VHDL语言描述该EDAC功能,使其兼容LEON3的AM-BA2.0总线,通过仿真试验验证了电路的可靠性。     

基于模糊PID控制的数控进给伺服系统仿真研究

针对数控机床进给伺服系统数学模型难以建立的问题,提出了一种模糊PID控制器,将其引入到数控进给伺服闭环控制中。并在Simulink环境下进行了仿真实验,结果表明,与传统PID控制相比,模糊PID控制改善了伺服系统动态性能,超调量小、鲁棒性强和稳态精度高。     

含偶氮苯结构树枝状化合物的合成与表征

以间二苯甲酸为原料,经多步反应合成5-[4-（羟乙氧基苯基）偶氮]-1,3-苯二甲酸;进一步与均苯三甲酰氯反应得到新型含偶氮苯结构树枝状化合物,通过FT—IR、UV—vis和。HNMR对中间体及树枝状产物进行了结构表征。TGA分析显示,5％失重温度为225℃,DSC测得树枝状化合物的玻璃化转变温度（嗜）为95．7℃。