摘要:

AbstractThe mechanism of polymerization of N‐carbonic anhydrides of α‐amino acids yielding polypeptides is discussed. Two aspects are considered ‐ (i) the “chain effect”, which occurs with suitable polymeric initiators and leads to high reaction rates with kinetics resembling those of simple emzymic reactions and (ii) polymerizations which become heterogeneous. The onset of heterogeneity in the latter case conincides with an increase in reaction velocity A study of the homogeneous polymerization of the N‐carbonic anhydride of γ‐benzyl‐Lglutamate in N,N‐dimethylformamide is described. Under suitable conditions this reaction show chain effect characteristics with a marked dependence on the optical configuration of the (polymeric) initiator and N‐carbonic anhydride. The chain effect, together with the associated specificity, may be effectively eliminated by addition of lithium perchlorate.Current ideas on the configuration of synthetic polypeptides are reviewed briefly. Some recent work on the optical rotation of poly‐β‐benzyl‐L‐aspartate is described; this shows,unter alia, the relative instability of the α‐helix form of this polymer in solution. the same instability is strikingly revealled by some experiments on the rate of the NH → ND re

ISSN:0025-116X    

DOI:10.1002/macp.1960.020350111

出版商:Hüthig&Wepf Verlag    

年代:1960

数据来源: WILEY

摘要:

AbstractDie Unterschung der Amylosesynthese mit Kartoffelphosphorylase ergab Befunde, die dem Reaktionsschema widersprechen. Die Polymerisationsgrade waren gering (DP 100‐200) und im Reaktionsverlauf konstant; die Molekulargewichtsverteilung war sehr breit und das Verhältnis der Zahl der Amylosemoleküle zu der der Startermoleküle ver‐hielt sich wie 17:1. Als Ursache der Abweichungen erwies sich eine äußerst geringe Beimengung an α‐Amylase, die durch Erhitzen auf 56°C inaktiviert werden kann.Synthesen mit Phosphorylase, die frei von α‐Amylase ist, entsprechen der Reaktions‐gleichung. Die Polymerisationsgrade steigen an, ohne obere Grenze, sie sind einstellbar durch die Starterkonzentration. Die Verteilung der Produkte entspricht bis zu ca. 20% Um‐satz der von POISSON berechneten. Die Proportionalität von Reaktionsgeschwindigkeit und Starterkonzentration beweist das Vorlliegen einer Mehrkettenreaktion.Beim phosphorolytischen Abbau erfolgt dagegen das Absinken der Polymerisations grade langsamer als nach dem Abbaugrad zu erwarten ist. Durch Vergleichsuntersuchun‐gen mit β‐Amylase läßt sich dieser Befund als eine mit dem Molekulargewicht zunehmende Bindungsfestigkeit zwischen Enz

ISSN:0025-116X    

DOI:10.1002/macp.1960.020350112

出版商:Hüthig&Wepf Verlag    

年代:1960

数据来源: WILEY

摘要:

AbstractThis article deals with the chemical properties of some modification of cellulose prepared by means of oxidizing and reducing agents. After a survey of relevant publications, a description is given of work carried out at the Finnish Pulp and Paper Research Institute, and in particular the investigations made by VIRKOLA, as yet un‐published. The last mentioned investigations are primarily concerned with the “dialcohol cellulose” obtained by borohydride reduction of dialdehyde cellulose. The results obtained by VIRKOLA show, amongst other things, that dialcohol cellulose, contrary to what is the case with dealdehyde cellulose, is rather stable in an alkaline solution, but does not withstand the influence of acids. The report also includes a comparison between hydrolysis of the different modifications of cellulosein an acid and an alkaline medium. Finally, by means of molecular fractionation investigations, it has been proved that the reaction between periodate and cellulose does not take place at regular distances in the cellulose chin, and that a further oxidation with intensified influence of periodate occurs in the immediate neighbouhood of the chain units already oxi

ISSN:0025-116X    

DOI:10.1002/macp.1960.020350113

出版商:Hüthig&Wepf Verlag    

年代:1960

数据来源: WILEY