http://www.vitaletherapeutics.org/nomncltr.htm
Vulnerable vitaletheine (VSH) and vitalethine (VSSV) are trivial nomenclatures derived from the commonly used terms, beta-alethine/beta-aletheine and cysteamine/cystamine (CSH/CSSC) nomenclatures. Vitaletheine (VSH) and its disulfide, vitalethine (VSSV), can both be hydrolyzed and inter-converted between their thiol (RSH) and disulfide forms (RSSR) to beta-aletheine/beta-alethine (ASH/ASSA) and cysteamine/cystamine (CSH/CSSC). Mixed disulfides are also possible, such as ASSC and VSSC, but VSSA has never been observed since it appears to go spontaneously to nearly all ASSA.