[Anionic copper: cupriacetic complex].

The application of a universal allyl linker, 9-O-(4,4'-dimethoxytrityl)-10-undecenoic acid, to the solid phase synthesis of RNA molecules is described. Use of this linker simplifies significantly the isolation and purification steps in RNA synthesis. The linker is universal in that it does not contain a nucleoside. The 3'terminal nucleoside is instead attached to the support in the first coupling step. The resultant RNA fragment is then obtained as the 3'-phosphate. The linker is base-stable, and thus all reagents used during deprotection can simply be washed away, leaving the RNA attached. Further, tritylated short fragments resulting from chain cleavage for any reason are also washed away before separation from the support. This linker is compatible with any current synthetic methodology and any amino functionalized support. Of course, silica supports would not be compatible with fluoride reagents. It could also be used to advantage for other applications. Because it is cleaved under conditions orthogonal to those used during many common reactions, the range of post-synthetic manipulations that can be carried out without cleavage from the support is extended significantly.

Acetates↗

PubMed1997

Proximity of acetate, manganese, and exchangeable deuterons to tyrosine YZ. in acetate-inhibited photosystem II membranes: implications for the direct involvement of YZ. in water-splitting.

The environment of the photosystem II YZ. radical, trapped in the "split-signal" form, is examined in acetate-treated PSII membranes using pulsed EPR methods. The split-signal line shape is simulated with dipolar and exchange couplings to the Mn cluster of 1260 and -28 MHz, respectively. The 1260-MHz dipolar coupling corresponds to a Mn-YZ. distance of 3.5 A in the point dipole limit. A 0.117-MHz dipolar coupling is observed between nonexchangeable deuterons of methyl-deuterated acetate and YZ.. This interaction is modeled with a 3.1-A distance between an acetate methyl group deuteron and the phenoxy oxygen of YZ*. Since acetate inhibition is competitive with Cl-, this result strongly suggests a close proximity between YZ. and the Cl- cofactor binding site. Analysis of pulsed ENDOR and ESEEM experiments investigating the proximity of deuterons exchanged into the vicinity of YZ. after incubation in 2H2O-enriched buffer demonstrates that YZ. trapped in the split-signal form participates in two hydrogen-bonding interactions, in contrast to YD*, which forms a single hydrogen bond. This result is inconsistent with a simple electron transfer role for YZ* and provides direct experimental evidence for a role for YZ* in proton or hydrogen atom transfer.

Acetates↗