摘要:

AbstractThe “hydrogen bond” or “hydrogen bridge” concept has proved to be one of the most useful structural concepts in modern science. The properties of substances containing hydrogen bonds depend on the strength, symmetry, and polarity of these bonds. These characteristics, in turn, are related to the effective electronegativities of the bridgehead atoms, the distance between these atoms, and the degree of coupling with other hydrogen bonds. Symmetrical hydrogen bonds exist in the FHF−and H5O 2+ions and in some acidic compounds. Coupled hydrogen bond systems exist, for example, in ice, liquid water, hydroquinone clathrates, starch, cellulose, polypeptides, nucleic acids, KH2PO4, and silicate hydrates. It is suggested that systems of coupled, nearly symmetrical, hydrogen bonds should be interesting subjects of furth

ISSN:0570-0833    

DOI:10.1002/anie.197101471

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY

摘要:

AbstractIn addition to the classical protective groups and linkage.methods for the synthesis of peptides, there are now a number of new techniques that allow the synthesis of fairly long peptide chains without racemization. In the present progress report, the diagnostic and therapeutic importance of the analogs obtainable by chemical synthesis is illustrated by some examples, particularly from the field of the peptide hormones secreted by the neurohypophysis, oxytocin and vasopressin, as well as corticotropins and releasing hormones. With the advance of synthesis technique, it will become possible to include fairly complicated molecules, such as insulin and even enzymes in such considerations.

ISSN:0570-0833    

DOI:10.1002/anie.197101521

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY

摘要:

AbstractRepressors are proteins that interact with inducers and operators to regulate the synthesis of enzymes in the cell. Lac repressor ensures that sufficient β‐galactosidase is available to the bacterium Escherichia coli, depending upon the amount of lactose present in the culture medium. It has proved possible to isolate lac repressor from E.coli. The present progress report describes how these discoveries were made, as well as the formation and mode of action of the repress

ISSN:0570-0833    

DOI:10.1002/anie.197101601

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY

摘要:

AbstractThe current ideas of organic chemists based on the work of Ingold and his school are applied to heterogeneous catalytic eliminations (mostly from haloalkanes and aliphatic alcohols). It is deduced from the activity of the catalysts, the reactivity of the substrates (reactants), and the primary product distribution that these eliminations proceed by a heterolytic mechanism similar to that involved in the liquid phase. The activity of the catalysts (salts and oxides) increases with increasing charge and decreasing radius of the cations and with increasing basicity of the anions. The reactivity of the substrates behaves in much the same manner as in the liquid phase. In contrast with the liquid‐phase reaction, the cis‐olefins are frequently favored as primary products. The stereospecificity of the reaction is determined from the relative strengths of the interactions between the catalyst cation and the leaving group X−, and between the catalyst anion and the leaving proton. Only trans elimination has so far been found in the concerted mech

ISSN:0570-0833    

DOI:10.1002/anie.197101721

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197101821

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197101831

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197101841

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197101862

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197101872

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197101881

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY