L-肌肽的合成研究

阐述了以β-丙氨酸及L-组氨酸为起始原料合成L-肌肽的合成工艺,并提出改进的工艺路线。该路线总收率在90%以上,质量分数高达99.5%以上,是低成本,高收率的合成方法,满足人们医疗保健要求。     

9种Na+通道mRNA在5个不同发育阶段大鼠16种组织中表达及变化趋势

电压-门控Na⁺通道由1个可单独发挥作用的α亚单位和2～4个起辅助作用的β亚单位构成,在可兴奋细胞动作电位的产生及传导等过程中起重要作用.采用RT-PCR法对5个不同发育阶段(P1、P9、P40、P80、P120)Wistar大鼠16种不同组织的9种Na⁺通道α亚单位及1种β亚单位的mRNA进行检测发现：同种类型Na⁺通道mRNA在大鼠不同组织中的表达不同,不同类型Na⁺通道mRNA在大鼠同一组织中的表达不同.其中,神经系统和心肌组织中Na⁺通道mRNA的表达最高,随着日龄的增加,Na⁺通道mRNA在不同组织中表达的变化趋势不同.Na⁺通道在全身组织中的广泛分布及随发育周期的不同变化趋势,为离子通道病的研究及治疗提供了理论基础.     

PTEN和β-cat在尖锐湿疣、Bowen＇s病和皮肤鳞癌中的表达及意义

目的：探讨PTEN和β-cat在尖锐湿疣、Bowen＇s病和皮肤鳞癌中的表达及意义。方法：采用免疫组化法检测蛋白PTEN和β-cat在正常皮肤、尖锐湿疣、Bowen＇s病、皮肤鳞状细胞癌（Scc）中的表达。结果：在正常皮肤、尖锐湿疣、Bowen＇s病、皮肤鳞状细胞癌（Scc）中PTEN蛋白的高表达率分别为100%,80.95%,46.67%,36.67%;β-cat蛋白的异常表达率分别为16.67%,30.16%,53.33%,70.00%,与正常皮肤组织相比,Bowen＇s病及Scc中PTEN蛋白的高表达率表达下降（P〈0.05,P〈0.01）;β-cat蛋白的异常表达率明显升高（P〈0.05,P〈0.01）。在Scc中两者的表达呈负相关（r=-0.416,P〈0.05）。结论：蛋白PTEN、β-cat在Scc的发生、发展中有重要的意义。     

Outsmarting metallo-beta-lactamases by mimicking their natural evolution

Metallo-β-lactamases (MBLs) confer antibiotic resistance to bacteria by hydrolyzing and thus inactivating β-lactam antibiotics. They have raised concerns due to their broad substrate spectra, the absence of clinically useful inhibitors, and their rapid dissemination. The resulting threat to public health is enhanced by their potential to evolve into even more efficient enzymes through mutation. This is based on the assumption that these enzymes are relatively novel and in the beginning of their natural evolution. Their ongoing evolution has been manifested by the isolation of improved enzyme variants from clinical isolates, and improved variants have been generated under controlled laboratory conditions. Our ability to mimic and eventually predict the evolution of MBLs will likely put us into a better position to effectively combat MBL-conferred antibiotic resistance. This review summarizes how various approaches in recent years have brought us closer to that goal.     

Thermochemical transformation of glucose to 1,6-anhydroglucose in high-temperature steam

An aqueous solution of glucose was reacted at temperatures from 200 to 400 degrees C under atmospheric pressure using a continuous flow reactor. For reaction temperatures above 300 degrees C, the liquid product yield was not sensitive to the temperature change; on the other hand, below 300 degrees C, it decreased rapidly with decreasing temperature. 1,6-Anhydro-beta-D-glucopyranose (AGP) and 1,6-anhydro-beta-D-glucofuranose (AGF) were the major components in the liquid product. The yields of AGP and AGF were 40% and 19%, respectively, at 360 degrees C and a feed rate of 0.5 mL/min. The optimum space time to produce AGP and AGF was about 0.2-0.4s under the present temperature conditions.     

Quantitative analysis of EGFR affinity to immobilized glycolipids by surface plasmon resonance

EGF-induced activation of EGFR tyrosine kinase is known to be inhibited by ganglioside GM3, its dimer, and other mimetics. However, details of the interaction, such as kinetic properties, have not yet been clarified. The direct interaction is now defined by the surface plasmon resonance (SPR) technique. To determine the affinity of EGFR for lyso-GM3 or lyso-GM3 mimetic, these glycolipid ligands were covalently immobilized onto a sensor chip, and binding affinities were investigated. Results of these studies confirmed the direct interaction of lyso-GM3 or its mimetic with EGFR. A strong interaction between EGFR and lyso-GM3 or its mimetic was indicated by increased binding of EGFR to glycolipid-immobilized surface, in an EGFR dose-dependent manner.     

Activation of the progesterone-signaling pathway by methyl-beta-cyclodextrin or steroid in Xenopus laevis oocytes involves release of 45-kDa Galphas

Treatment of Xenopus laevis oocytes with cholesterol-depleting methyl-β-cyclodextrin (MeβCD) stimulates phosphorylation of mitogen-activated protein kinase (MAPK) and oocyte maturation, as reported previously [Sadler, S.E., Jacobs, N.D., 2004. Stimulation of Xenopus laevis oocyte maturation by methyl-β-cyclodextrin. Biol. Reprod. 70, 1685-1692.]. Here we report that treatment of oocytes with MeβCD increased levels of immunodetectable 39-kDa mos protein. The protein synthesis inhibitor, cycloheximide, blocked the appearance of Mos, blocked MeβCD-stimulated phosphorylation of MAPK, and inhibited MeβCD-induced oocyte maturation. These observations suggest that MeβCD activates the progesterone-signaling pathway. Chemical inhibition of steroid synthesis and mechanical removal of follicle cells were used to verify that MeβCD acts at the level of the oocyte and does not require production of steroid by surrounding follicle cells. Cortical Gα_s is contained in low-density membrane; and treatment of oocytes with progesterone or MeβCD reduced immunodetectable levels of Gα_s protein in cortices and increased internal levels of 45-kDa Gα_s in cortical-free extracts. Dose-dependent increases in internal Gα_s after treatment of oocytes with progesterone correlated with the steroid-induced maturation response, and the increase in internal Gα_s after hormone treatment was comparable to the decrease in cortical Gα_s. These results are consistent with a model in which release of Gα_s from the plasma membrane is involved in activation of the progesterone-signaling pathway that leads to amphibian oocyte maturation.     

Eye formation in the absence of retina

Eye development is a complex process that involves the formation of the retina and the lens, collectively called the eyeball, as well as the formation of auxiliary eye structures such as the eyelid, lacrimal gland, cornea and conjunctiva. The developmental requirements for the formation of each individual structure are only partially understood. We have shown previously that the homeobox-containing gene Rx is a key component in eye formation, as retinal structures do not develop and retina-specific gene expression is not observed in Rx-deficient mice. In addition, Rx−/− embryos do not develop any lens structure, despite the fact that Rx is not expressed in the lens. This demonstrates that during normal mammalian development, retina-specific gene expression is necessary for lens formation. In this paper we show that lens formation can be restored in Rx-deficient embryos experimentally, by the elimination of β-catenin expression in the head surface ectoderm. This suggests that β-catenin is involved in lens specification either through Wnt signaling or through its function in cell adhesion. In contrast to lens formation, we demonstrate that the development of auxiliary eye structures does not depend on retina-specific gene expression or retinal morphogenesis. These results point to the existence of two separate developmental processes involved in the formation of the eye and its associated structures. One involved in the formation of the eyeball and the second involved in the formation of the auxiliary eye structures.