No abstract

A procedure is described for the simultaneous separation of all the peptides (other than those present in trace amounts) contained in the venom of the common European honey bee (&is mellifera). Three new peptides have been isolated: one is a fragment of the known peptide melittin. Some properties of the peptides are described.

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In neutral or acidic solution trimethyl phosphate undergoes hydrolysis with carbon-xygen bond fission, and acid-catalysis is not observed. The second-order reaction with hydroxide ions, on the other hand, proceeds with phosphorus-oxygen bond fission. Similarly triphenyl phosphate is hydrolysed with phosphorus-oxygen bond fission in alkaline solution. The latter reaction, which has a low activation energy (ca. 10 kcal. mole-l), has been shown not to involve isotopic exchange a t the phosphoryl oxygen atom. SIMPLE trisubstituted phosphate esters are known to be relatively alkali-labile : lP3 with the exception of an investigation of trimethyl phosphate

The hydrolysis of dimethyl phosphate has been investigated over a range of acidities, pH 5 to solution in B~-perchloric acid. Two hydrolytic mechanisms have been identified, both proceeding largely with carbonoxygen bond fission but involving respectively the neutral species and the conjugate acid. Hydrolysis in strongly alkaline solution also proceeds with carbon-oxygen fission. The mechanisms of these reactions are discussed.PART I of this series * reported a study of the mechanisms of hydrolysis of monomethyl dihydrogen phosphate. This paper is concerned with a similar study of dimethyl hydrogen phosphate.It has been known for some time that dialkyl phosphates are hydrolysed readily only in strongly acidic so1utions.l The only quantitative studies so far reported, however, are those of Westheimer and his c o -~o r k e r s .~*~~~ They investigated the hydrolyses of dibenzyl phosphate in some detail, and found that in the range of acidity pH 8 to 1.0M-acid there were two hydrolytic reactions, involving, respectively, the neutral and the conjugate acid species. The monoanion species, unlike that of phosphate monoesters, was relatively unreactive. The hydrolysis of dimethyl phosphate in strongly alkaline solution was also inve~tigated.~ Under these conditions hydrolysis was found to be of the first order in hydroxide ion and exceedingly slow, which is consistent with the generalisation that alkaline lability in dialkyl hydrogen phosphates occurs only when the molecule contains a hydroxyl group in proximity to the phosphoryl function.