Chemical ionzation mass spectra of amino acids and derivatives. Occurrence and fragmentation of ion-molecule reaction products

The Chemical ionization mass spectra of free amino acids, their amides, methyl esters and Na-acetyl derivatgives, using methane as reagent gas, are presented, The occurrence and fragmentation of ion-molecules reaction products are discussed. A preference for a head to tail, configuration of the association complex [2M + 1]+ is postulated to esplain promienent fragmentation pathways of this complex. Interesting fragmentation pathways have been found with onithine, arginine and citrulline

Permethylation of methionine-containing oligopeptides for sequence analysis by mass spectrometry

Methionine-contg. oligopeptides were permethylated on the nanomolar level. Under the conditions developed, the formation of sulfonium iodide and cyclopropane derivs. during the permethylation reaction was avoided. The mass spectra presented contain complete sequence information. [on SciFinder (R)

A laboratory procedure for the acetylation and permethylation of oligopeptides on the microgram scale

The amino acid sequence of oligopeptides can be determined from the mass spectra of their volatile derivatives. A general procedure for the N-acetylation and N,O,S-permethylation of unknown peptides that do not contain arginine is described. The procedure is illustrated by the derivatization of lysyl-tyrosyl-glutamic acid. The mass spectrum of the resulting Na, N' -diacetyl-Na, N'-dimethyllysyl-Na, O-dimethyltyrosyl-Na-methyl glutamic acid , ß dimethyl ester (I)1 is given

Modification, permethylation, and mass spectrometry of arginine-containing oligopeptides at the 100 nanomolar level

The amino acid sequence of arginine-contg. oligopeptides, including bradykinin, was detd. by mass spectrometry. The guanidino groups of the arginine residues in 100 nmoles of peptide were reacted with acetyl-acetone under mild conditions to produce Nd-2-(4,6-dimethyl)pyrimidylornithine residues. N-Acettylation and N,O-permethylation then produced peptide derivs. that were suitable for vaporization. This procedure makes arginine-contg. oligopeptides accessible for mass spectrometric sequence anal. [on SciFinder (R)

The selective response of photographic emulsions to ion structure

The simultaneous exposure of a photographic emulsion to naphthalene and Xe ions, i.e. polyat. and monoat. ions of the same nominal mass, demonstrated a 250% higher emulsion response to the naphthalene mol. ion than to Xe+. Also, the more compact naphthalene mol. ion tended to give a darker image on the emulsion than the more conformationally mobile n-nonane ion. However, the emulsion response was essentially the same for the naphthalene and quinoline ions, which have similar shape and size

Ion detection in mass spectrometry. The dependence of ion-sensitive plate response on ion structure and composition

The response of various types of ion-sensitive plates as a function of ion structure and composition has been investigated. Several ions of similar nominal mass and equal energy covering a wide variation in structure have been studied. It has been found that the response of the emulsion is dependent on the structure and composition of the impinging ion. The selectivity of emulsion response to molecular ions of variant structure is discussed in terms of a mathematical model proposed by Honig. The experimental results suggest that monoatomic ions and ions generally containing a smaller number of atoms produce darker photographic images than ions of the same mass and energy, but of more polyatomic nature. Ions of similar structure produce images of equal relative intensity but a dependence on chemical composition is also apparent. The evaporated silver bromide plates exhibited a linear relationship of total peak area versus log relative exposure over a dynamic range of at least 100

The use of mass spectrometry in peptide chemistry

A review with 16 refs. Methods are detailed for derivatizing peptides (mg quantities) in order to provide sufficient volatility for mass spectrometry (at least 10-5 mm vapor pressure at 300 Deg is required). Three steps are used in producing the desired derivs.: (a) arginine side chains are converted to dimethylpyrimidyl ornithine by reaction with acetylacetone; (b) free amino groups are acetylated by reaction with Ac2O in order to avoid quaternization during permethylation; and (c) N, O, S permethylation is used to replace all H atoms not bound to C with a Me group by reacting the peptide with methylsulfinylmethide carbanion (DMSO-) to produce a peptide polyanion and then by adding MeI for methylation. With each mass spectrum obtained, the amino acid sequence is derived via a computer program similar to that of K. Biemann, et al. (1966). [on SciFinder (R)