title: A spectrophotometric study of the reaction of boro-hydride with trinitrophenyl derivatives of amino acids and proteins.
abstract: The absorption spectra of trinitrophenyl derivatives of poly(L-lysine) and L-asparaginase undergo irreversible changes in the presence of KBH4. The spectra of trinitrophenyl derivatives of N-acetyl-L-lysine and N-acetyl-L-cysteine are also affected by the addition of the reducing agent. A broad absorption band with a maximum at 426 nm appears in the presence of low concentrations of borohydride with a concomitant decrease in absorbance of the 346 nm band which is characteristic of 1-substituted 2,4,6-trinitrophenyl compounds. In the presence of higher concentrations of KBH4 the long wavelength band becomes less broad as the maximum is shifted to 410 nm and the 346 nm band completely disappears. Similar spectral changes were observed in the presence of Na2SO3 although these were reversible upon removal of the sulfite by dialysis. Based on the spectral similarities with sulfite and hydroxide adducts, we suggest that the 426 nm maximum represents a 1:1 adduct formed between the trinitrophenyl moiety and a hydride ion while the band at 410 nm is assigned to the 1:2 adduct.
mesh_terms: D000596:Amino Acids; D001215:Asparaginase / Q000378:metabolism; D001665:Binding Sites; D001894:Borohydrides; D007700:Kinetics; D009578:Nitrobenzenes; D011485:Protein Binding; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D014301:Trinitrobenzenes
chemical_list: D000596:Amino Acids; D001894:Borohydrides; D009578:Nitrobenzenes; D014301:Trinitrobenzenes; D001215:Asparaginase