Unidentified Groups

In 1971, adrenodoxin, an iron-sulfur protein with a single tyrosine residue and no tryptophan was shown to fluoresce at 331 nm upon 280-nm excitation at neutral pH/20 1 On cooling from room temperature to 77 K, the emission maximum shifts to 315 nm. The redox state of the iron does not have any effect on the tyrosine emission. From these results, an exciplex between the excited singlet state of tyrosine and an unidentified group was suggested as the cause of the anomalous emission energy/2031 Later studies have shown that the excitation spectrum is a red-shifted tyrosine spectrum, that removal of the iron to form the apoprotein has no effect on the emission, and that heat, low pH, guanidine hydrochloride, urea, and LiCl all cause the emission... 

Mining wives have no public profile. Outside the resources sector they are an unidentifiable group, unseen and unheeffd. (She is) a dependent spouse whose willingness to mainteiin male privileges for husbtmd and company had been taken for granted for many years. 

If, however, the 7-position is blocked by a methyl group, then a more complex reaction ensues involving ring contraction, methyl migration and loss of the nitrogen function to give 4,6.6-trimethyl-2,3,5-triphenylcyclohexa-2,4-dienone (12% mp 198 C) and other unidentified... 

Our group has exploited 4-phenylthio-l,3-dioxanes as convenient precursors to 4-lithio-l,3-dioxanes [45,65-69]. 4-Phenylthio-l,3-dioxanes 184 were originally prepared from -silyloxy aldehydes 183 [65] (Eq. 28). Lewis acid-promoted addition of phenylthiotrimethylsilane gave an unstable thioacetal intermediate, which could be converted in situ to the corresponding 1,3-dioxane. Yields for this process are variable, as the product is unstable under the conditions of its formation. The reaction slowly evolves to a mixture of the desired product, the phenylthio acetal of 183, the phenylthio acetal of acetone, and a variety of other unidentified products. 

Some forms of protein may have been possessed by the common ancestor of nematodes and vertebrates but subsequendy lost in one line some may be entirely new inventions of either group, modified from an unidentifiable common precursor. 

There were substantial problems with impurities and degassing in the initial time-resolved IR measurements on Cr(CO)6 in solution. The spectroscopic results were very encouraging, but an unidentified Cr(CO)sX species (X = impurity) was observed (60). The system has now been examined in detail by the Miilheim group (96), who overcame the earlier experimental problems. 

Group VIA (Cr, Mo, W). y-Radiolysis studies have been carried out for the simple hexacarbonyls (31,32) and for certain carbonyl iodides (33) and cyclopentadienyl carbonyl iodides (34). In the case of the hexacarbonyls (31,32), two free-radical products have been detected and characterized for Cr(C0)6, weak unidentified EPR signals have been observed for Mo(C0)6, but irradiated W(C0)6 apparently contains no detectable paramagnetic centres. 

Poisoning and sometimes death from eating (unidentified) mushrooms is well known. In particular, Amanita sp. are particularly dangerous, with much emphasis on the death cap fungus , Amanita phalloides.24 The best known toxins are the amatoxins and phallotoxins, which are complex, bicyclic peptides. An unusual feature relates to sulfur a tryptophan (or substituted tryptophan) unit is linked to a cysteine sulfur at the carbon atom next to the NH group of the pyrrole ring, forming the unit, -CH2-S-C(NH)=C, e.g. in... 

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