Increasingly grim environmental pollutions are closely related with the occurrence and development of diseases. However, it’s obscure how stress disturbs normal physiological process, then endogenous reactive species mend cases. Hypoxia/reperfusion (H/R), a common intractable injury in aquaculture clinic, can induce oxidative ultimately cause irreversible to organism. Cysteine (Cys) plays essen...

We report the direct observation of intramolecular hydrogen atom transfer reactions (tautomerization) within a single porphycene molecule on a Cu(110) surface by scanning tunneling microscopy. It is found that the tautomerization can be induced via inelastic electron tunneling at 5 K. By measuring the bias-dependent tautomerization rate of isotope-substituted molecules, we can assign the scanni...

Dihydrofolate reductase (DHFR) catalyzes the NADPH-dependent reduction of dihydrofolate (DHF) to tetrahydrofolate (THF). An important step in the mechanism involves proton donation to the N5 atom of DHF. The inability to determine the protonation states of active site residues and substrate has led to a lack of consensus regarding the catalytic mechanism involved. To resolve this ambiguity, we ...

A metal ion that attaches to a peptide backbone has the choice of binding to an amide carbonyl oxygen atom or to an amide nitrogen atom by replacement of the amide proton. Coordination to the nitrogen atom is normally accompanied by elimination of the proton, thereby resulting in deprotonation of the ligand. An alternative possibility, not involving deprotonation, is the unusual amide/iminol ta...

In his book The Double Helix, James Watson describes an early proposal for DNA structure in which equal bases pair with each other. He writes: ‘‘My scheme was torn to shreds the following noon. Against me was the awkward chemical fact that I had chosen the wrong tautomeric forms for guanine and thymine.’’ This fact was pointed out to him by the American crystallographer Jerry Donahue who ‘‘ . ....

We present calculations for the mechanism and the barrier heights of tautomerization of adenine. We find various pathways for the 9(H) <--> 7(H) and 9(H) <--> 3(H) tautomerization. One mechanism for the 9(H) --> 7(H) tautomerization involves an sp(3)- or carbene-type intermediate, whereas the other proceeds via imine intermediates. Tautomerization from the 9(H) tautomer to 7(H) or 3(H) is predi...

single walled nanotubes (swnt) are common interested nanovehicle to make biosensors more sensitive.carbon nanotubes (cnts) have many distinct properties make them to be exploited to develop the nextgeneration of such nano sensors .the keto-enol tautomerization is one of the most common investigatedsubjects of isomerism in this regards, sensors are devices that are able to detect and change the ...

The tautomerization of Criegee intermediates via a 1,4 β-hydrogen atom transfer to yield a vinyl hydroperoxide has been examined in the absence and presence of carboxylic acids. Electronic structure calculations indicate that the organic acids catalyze the tautomerization reaction to such an extent that it becomes a barrierless process. In contrast, water produces only a nominal catalytic effec...