A comparison ofl-asparaginase fromErwinia aroideae and fromEscherichia coli: Biochemical and biological properties

Zusammenfassung l-Asparaginase wurde ausErwinia aroideae gewonnen und durch Fraktionierung wie Fällungsschritte und Chromatographie um das 500fache angereichert. Das Enzym zeigt keine immunologische Kreuzreaktion mitl-Asparaginase ausEscherichia coli. Durch Acylierung lässt sich das basische Proteinl-Asparaginase ausE. aroideae in ein saures Protein unter weitgehendem Erhalt der Enzymaktivität überführen.     

On the distribution of plasma L-asparaginase

Summary The guinea-pig,Cavia porcellus, is unusual in possessing plasma L-asparaginase, an enzyme with anti-tumor activity. 21 additional species have been examined as to the presence of this enzyme: the results confirm and extend its remarkably limited species distribution.This work was supported in part by grant GM/CA 25378 from the National Institute of General Medical Sciences, National Institutes of Health.We are grateful to dr Hanna Hensch, Philadelphia Zoological Garden, and Ms Joan Whitla and Dr Richard J. Montali, National Zoological Park/Smithsonian Institution, for samples of frozen serum.To whom correspondence should be addressed.     

On the distribution of plasma L-asparaginase

The guinea-pig, Cavia porcellus, is unusual in possessing plasma L-asparaginase, an enzyme with anti-tumor activity, 21 additional species have been examined as to the presence of this enzyme: the results confirm and extend its remarkably limited species distribution.     

Antinicotinic properties of papaverine in guinea-pig taenia coli

Zusammenfassung Mit Hilfe der Saccharosetrennwand-Methode wird nachgewiesen, dass Papaverin antinikotinisch an der glatten Muskulatur (Taenia coli) des Meerschweinchens wirkt.     

Crystallization of RNA

Even as the number of RNA structures determined and under study multiplies, the critical step in X-ray diffraction analysis, growth of single well-ordered crystals, remains at the boundary between art and science. Recent advances in methods of RNA synthesis, purification, and characterization, as well as empirical and technical improvements in crystallization techniques, the development of cryo-crystallography, and the wider availability of bright, tunable, X-rays from synchrotron sources are improving the chances of obtaining RNA crystals suitable for X-ray structural analysis. In this review, we summarize the current status of the design, preparation, purification, and analysis of RNA for crystallization and describe the latest approaches to obtaining diffraction-quality crystals. Received 17 October 2000; revised 6 December 2000; accepted 8 December 2000     

Structural and functional properties of porin channels in E. coli outer membranes.

Porin is a channel-forming, voltage-dependent protein of E. coli outer membranes. It exhibits relatively unspecific molecular sieve properties (exclusion size 600 Da). The trimer (110 kDa) consists of three identical polypeptides. Its secondary structure is mostly beta-structure, part of which can be visualized by electron microscopy to form a single beta-pleated sheet near the protein-lipid interface of the trimer. This folding pattern is significantly different from those of the reaction centers and of bacteriorhodopsin. Moreover, it contains many polar and ionizable side chains. It is argued that local as well as global electroneutrality, and complete saturation of the entire hydrogen bonding potential not only allow the protein to reside in the hydrophobic membrane core, but also confer upon it its unusual stability.     

聚合物超薄膜结晶相关的形貌形成及链行为

聚合物超薄膜结晶是高分子物理领域的一个新研究课题,近来已引起人们的关注,其为人们在真实时空下研究聚合物结晶及相关链行为提供了可能。聚合物超薄膜结晶与膜厚(D)有很强的相关性,尤其是D<20nm的薄膜在结晶形貌和结晶动力学方面与本体结晶差别很大。已有的结果主要集中在结晶形貌、晶体尺寸、晶体生长速度和习性、晶体的熔融和结晶度等方面,涉及温度、膜厚、基片性质和膜的组成和结构对结晶的影响;然而,有些实验结果和解释彼此不完全一致,甚至有时相互矛盾。本文综述和讨论了近年来在超薄膜结晶方面的研究,重点在于结晶形貌的形成和相关的聚合物链行为。