Triplet labeling

Figure 3.16. Temperature dependences of the parameters of physical labels on chromotophores from R. rubrum (a) Shematic diagram of the locations of spin and triplet labels, (b) Experimental data t n is the characteristic time of electron transfer from the reduced primary acceptor to the oxidized primary donor (Likhtenshtein, et al., 1996). Reproduced with permission.

The rate of another important process, the recombination of the primary product of the charge separation, i.e. the reduced primary acceptor (QA ) and oxidised primary donor, bacteriochlorophyl dimer (P+), falls from 103 to 102 s 1 when dynamic processes with uc = 103 s 1 monitored by the triplet labelling method occur. Very fast electron transfer from P+ to bacteriochlorophyl (Bchl) and from (Bchl) to QA does not depend on media dynamics and occurs via conformationally non-equilibrium states (Fig. 3.16). 

Druzhinin, S.Yu., Fogel, V.R., Syrtsova, L.A., Likhtenstein, G.I. and Kotelnikov, A I. (1986) Study on the cofactor center localization in nitrogenase by triplet labeling method, Biofizika. 31, 16-21. 

Vogel, V.R. Rubtsova, E. T. Kotel nikov, A. I. Likhtenshtein, G. I. (1986) Study of protein collisions in solutions by triplet labels, Bioflzika 31, 152-154. 

A triplet label for membrane proteins Eosme-malemide... 

The group 85 contains one sextuplet representation which in As splits into two triplets, labeled as the icosahedral Ti and T2 irreps. Clearly, since the icosahedral group cannot act transitively on a set of seven elements, we should not expect that it can host a sixfold degeneracy. In the context of the graph-theoretical JT theorem, this makes these triplets exceptional, since they cannot be related to the... 

The reader is reminded that the labels A, B, C rather than a, b, c for triplet states of N2 do not follow the usual convention. 

Figure 7-2H. (a) ll-l ADMR and (b) A-PADMR spectra of u-6T film. The peaks of polarons, bipolarons, and triplet cxei-(ons are labeled. 

The subsets of d orbitals in Fig. 3-4 may also be labelled according to their symmetry properties. The d ildxi y2 pair are labelled and the d yldxMyz trio as t2g. These are group-theoretical symbols describing how these functions transform under various symmetry operations. For our purposes, it is sufficient merely to recognize that the letters a ox b describe orbitally i.e. spatially) singly degenerate species, e refers to an orbital doublet and t to an orbital triplet. Lower case letters are used for one-electron wavefunctions (i.e. orbitals). The g subscript refers to the behaviour of... 

Orbital phase continuity in triplet state. The orbital phase properties are depicted in Fig. 5c. For the triplet, the radical orbitals, p and q, and bonding n (a) orbital are donating orbitals (labeled by D in Fig. 5c) for a-spin electrons, while the antibonding jt (a ) orbital (marked by A) is electron-accepting. It can be seen from Fig. 5c that the electron-donating (D) radical orbitals, p and q, can be in phase with the accepting (a ) orbital (A), and out of phase with the donating orbital, Jt/a (D) at the same time for the triplet state. So the orbital phase is continuous, and the triplet state of 1,3-diradical (e.g., TMM and TM) is stabilized by the effective cyclic orbital interactions [29, 31]. 

In order to obtain more insights into the biosynthetic mechanism, [Me- C-Me-d ] double-labeled methionine was fed to the organism. The C-NMR spectrum of resulting neosaxitoxin showed a clean triplet for C-13 beside the natural abundance singlet. The result indicated that only one deuterium was left on the methylene carbon. 

The ion-triplet oxidises I in the slow step to yield -Iz . The non-participation of any ligand substitution step is confirmed by the absence of any incorporation of activity from added C-labelled free cyanide ion into the product ferrocyanide ... 

Deoxycytidine (dCyd) (14 in Scheme 2) is also an excellent target for one-electron oxidation reactions mediated by triplet excited menadione. On the basis of extensive identification of dCyd photooxidation products, it was concluded that this nucleoside decomposes by competitive hydration and deprotonation reactions of cytosine radical cations with yields of 52% and 40%, respectively [53]. It was also found, on the basis of 180 labeling experiments, that hydration of cytosine radical cations (15) predominantly occurs... 

Methylene insertion into C—H bonds is believed to be concerted for the singlet species and stepwise for the triplet.<164,156) The C—H insertion of methylene into the 14C-labeled isobutylene shown below results in 92% unrearranged isopentenes and 8% rearranged isopentene [Eq. (11.22)]. Assuming that an additional 8% of the unrearranged isopentene arises from the stepwise addition, it is clear that 84% of the insertion products result from insertion by singlet methylene and 16% by triplet methylene ... 

Figure 15 shows this same expanded region when di-methyl terephthalate is used as the monomer. The only difference is the sharp single peak labelled g, which arises from residual methyl ester end groups. This resonance sits on top of the triplet arising from the -CH2OH (f) end (at 400 MHz) and, therefore, deconvolution software is used to measure these residual methyl ester ends. 

Fig. 4 Esr spectra of high-spin trianthrylene [21a] at 120 K in MTHF/K A, biradical triplet state [21a]2- (labelled O) B, triradical quartet state [21a]3- (labelled ) C, biradical triplet state [21a]4- (labelled ).

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