Despite numerous experimental and theoretical studies, the proton transfer accompanying the oxidation of 2'-deoxyadenosine 5'-monophosphate 2'-deoxyadenosine 5'monophosphate (5'-dAMP, A)i ss till under debate. To address this issue, we have investigated the oxidation of A in acidic and neutral solutions by using transient absorption (TA) and time-resolved resonance Raman( TR 3 )s pectroscopic methods in combination with pulse radiolysis. The steadystate Raman signal of A was significantly affected by the solution pH, but not by the concentration of adenosine (2-50 mm). More specifically,t he A in acidic and neutral solutions exists in its protonated (AH + (N1 + H + )) and neutral( A) forms, respectively.O nthe one hand, the TA spectral changes observed at neutral pH revealed that the radical cation (AC + )g enerated by pulse radiolysis is rapidly converted into AC(N6ÀH) through the loss of an imino protonf rom N6. In contrast, at acidic pH (< 4), AHC 2 + (N1 + H + )g enerated by pulse radiolysis of AH + (N1 + H + )d oes not undergo the deprotonationp rocess owing to the pK a value of AHC 2 + (N1 + H + ), whichi sh igher than the solutionp H. Furthermore, the resultsp resented in this study have demonstrated that A, AH + (N1 + H + ), and their radical species exist as monomers in the concentrationr ange of 2-50 mm.C ompared with the Ramanb ands of AH + (N1 + H + ), the TR 3 bandso fAHC 2 + (N1 + H + )a re significantly down-shifted, indicatingadecrease in the bond order of the pyrimidine and imidazole rings due to the resonance structure of AHC 2 + (N1 + H + ). Meanwhile, AC(N6ÀH) does not show aR aman band corresponding to the pyrimidine + NH 2 scissoring vibration due to diprotonation at the N6 position. These resultss upport the final products generated by the oxidation of adenosine in acidic and neutrals olutions being AHC 2 + (N1 + H + )a nd AC(N6ÀH), respectively.
Controlling the conformationa nd functiono fb iomolecules through photoregulators holds great promise as a spatiotemporally controllable tool for disease control.I na ddition, introducing photoregulators into biomoleculesh as also found applicationsi nc onstructings martn anomaterials. In spite of the astonishing advances that have been made in the past few years, realizing highly controllable and efficient regulation over the conformation and functiono fb iomolecules under physiological conditionsi ss till challenging. Herein,s ulfonated pyrene SPy was synthesized and used as ap hotoregulator to control the looping of single-stranded DNAs (ssDNAs) in aqueous solution.Due to its water solubility, SPy merits use in the study of biomolecules in aqueous solution.T he looping of the doubly SPy-modified ssDNAs is stimulated by irradiation and regulated by SPy.P hotoionization generatest he radicalc ation of SPy (SPyC + ). The association of SPyC + + with its neutralc ounterpart, SPy,g ives rise to the dimer radicalc ation of SPy (SPy 2 C + + ). During the association process, the stabilization energy released to form SPy 2 C + + provides ad riving force for the looping of ssDNAs. Conversely,t he formed loop conformationsw ere trapped by the formation of SPy 2 C + + ,a nd this allowed the looping dynamics to be investigated. The results reported herein suggest potential of SPy as ap hotoregulator for controlling the conformationa nd function of biomolecules under physiological conditions.[a] J.[a] Immediately formed SPy 2 C + + component. P static = DOD t = 10 ns /DOD max .
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