February 10, 1945. br, de Monod, Ltinstitut Pasteur, Paris, franca. ‘ Wear Jacj.ues- vome wdaltoge-negative nutaite were despatched to you several days «zo. I believe thay ineluded the following: wel. witty — tutant of X53 (Ame i iy beady) em W330 Lae-reversion of Wel Qfheref ve, TeleD,~ilal—~Lucd) Wie20 Malo~ mutant of 58-161 (B--) V. slow positive. 56 aby mutant of X89 (BeV,") aul allelic aith J-L. (m6 isle mutant of G40 . hut allelic with “-L. w-L02 0 Malye mutant of LLU (T-u-5j)-). wot ciielic with u-1 or 60. not yet tested with 20, 4nrough an oversight, I ao not kimw whether these vere sent also: welOQE Tiucese-nesaetive muvant of Y-1C, JabS9 4 Gon- or poor-fermenting mutant of i-Lu #172 «4 gidiconiceymeltose~ mutant of Y-1C. I trust theses wili be of some use to you. 1 have a nuwder of others, out until the genatit analysis is eoapletsd, we would not iknow which of then vere redundant. You have the wild type (re fernentation) prosentters of these strato. Your findings ca the lactase of coll aL are aost interesting. I nad pienned on toying the sars sort of thing with h-L2— nerhaps you could coliss me sith a suamiry of your methods, or even better why aot repeat your praparations using Kel2. If thers is but a single enzyne, sone of my results become aost perplexing. a examp.e, wae wlid type splite buty.~b-galactosids as we}l us leotose. Some Lace matants cit still split the galactosids, anile others cunnot. In a further examination of cross-adaptations in K-12, 1 fini the following? Lactost-adantec ara zilactcaeeadpptad, as expscted; gulactose-adapted sasn to adapt to lactose-much more quickly than cells grovn on glucose, Finuily, calactose ang l-arabincsse show con:lete cross-adaptation, although I have some mutants which sre galactose- Sub arablnsset. adaptation ts giucchate Is avecifie. Dearabino: (the direct decarboxylation derivative) is not utilized. I had oceasion to test « commercisl preparation (schwarz, ‘.Y.) of fraatose diphosapiats, sad noted that it was us active