Structure biotin sulfone

Figure 2 Structure of (-)biotin sulfoxide, (+)biotin sulfoxide, and biotin sulfone.

Growth-inhibitions by compounds structurally related to biotin have been observed. These are different in kind from the action of the antibiotin factor, where an inactive protein complex is formed. These structurally related anti-metabolites include biotin sulfone and desthiobiotin, their activities being related to the nutritional requirements of the organ-... 

A water-soluble analog of NHS-biotin containing a negatively charged sulfonate group on its NHS ring structure also is available. Sulfo-NHS-biotin may be added directly to aqueous reactions without the need for organic solvent dissolution. A concentrated stock solution may be prepared in water to facilitate the addition of a small quantity to a reaction, but hydrolysis of the NHS ester will occur at a rapid rate, so the solution must be used immediately. 

The structures and hydrolysis and aminolysis rates of some investigated M-PEG and other esters used in protein modification are shown in Table 1. Rates of reaction are influenced both by the nature of the leaving group and the pKa of the acid moiety. In the rates of biotin active esters, the koH- in min (i.e. rate constants for hydroxide caused hydrolyses) are 1.46 x lO for sulfo-N-hydroxysuccinimide, 2.28 x 10 for N hydroxysuccinimide, and 8.00 x 10 for hydroxy-2-nitrobenzene-4-sulfon-ic acid. The respective ti/2 s for hydrolysis are 26.9 min., 43.4 min., and 320 min. This order of magnitude difference is also reflected in the aminolysis rate constants (using as model amine 6-aminocaproic acid) which are 5.01 x 10, 7.71 x 10 and 3.16 x 10 min", respectively. The rate constant ratios for amine over hydroxide become 3.38, 3.43, and 3.95, which confirms that an improved ratio, and thereby better selectivity for protein amino groups can be obtained with an ester, such as HNSA, that reacts more slowly, and is less sensitive to buffer-catalyzed hydrolysis, as compared to N-hydroxysuccinimide ester. 

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