The distant shielding effect in trinucleoside diposphates
A comparative study on the proton magnetic resonance of the dinucleoside monophosphates TpT, dApT, TpdA, the trinucleoside diphosphates dApTpT, TpTpdA, and poly T has been made. The purpose of this investigation was to establish whether in a trimer the proton chemical shifts of one terminal residue are influenced by the magnetic anistropy of the other terminal residue. The conformation of the trimers was first studied and shown to the similar to that of the corresponding dimer, except that of the percentage of the lefthanded conformers in the population of the trimers is probably lower than in the population of the dimers. The methylprotons, H‐6, and H‐1′ of the 3′‐terminal T residue in TpTpdA (or the 5′‐terminal T residue in dApTpT) are found to be more upfield than the same protons on the dimer TpT up to a magnitude of about 0.1 ppm. The shielding of these protons of the terminal T(s) in these trimers is even larger than those corresponding protons in the poly(T) at the same condition. From these results, it is concluded that a distant shielding effect is exerted by the 5′‐terminal. A residue (or by the 3′‐terminal A residue) on the other terminal residue in the trimers studied.
Light-induced free-radical reactions of nucleic acid constituents. Effect of sequence and base--base interactions on the reactivity of purines and pyrimidines in ribonucleotides.
The reaction with 2-propanol of purines and pyrimidines, induced photochemically with light of lambda greater than 300 nm and di-tert-butyl peroxide as an initiator, was applied to a variety of adenosine-, guanosine-, and uridine-containing ribonucleotides in order to determine the rules which govern the reactivity of the heterocyclic bases of nucleotides. The reactivity of the purine moieties was found to depend on the conformation of the appropriate nucleotide (anti or syn) and on the site of binding of the phosphate group to the ribose moiety. Adenosine moieties (assuming an anti conformation) blocked at their 3'-hydroxyl reacted faster than those blocked at their 5'-hydroxyl. The reactivity of the guanosine moieties (tending to assume a syn conformation) was independent of the site of binding of the phosphate. The uridine moieties of the various nucleotides exhibited a wide range of reactivity. A correlation between the reactivity of the uridines and their involvement in stacking interactions with next- and second-neighboring purines could be made. Thus, the uridine moieties of U-U-U, G-U, U-G, A-U-A, and A-U-G were reactive, while those of A-U and A-U-U were unreactive. The relative reactivity of uridine moieties of nucleotides can, therefore, be used as a measure of the extent of pyrimidine-purine stacking and vice versa.
Experimental study on ground vibration of blasting the boulder with tandem shaped charging warhead
Hazardous effects of blasting the boulder with the new breaking-blasting equipment-tandem shaped charging warhead are mainly air shock wave, seismic wave and blast slung shot. Blast-induced ground vibration is one of the inevitable effects and may cause substantial damage to nearby structures. Started from the formation process and mechanism of ground vibration to study the seismic wave, the research attained curve of vibration velocity of monitoring points by TC-4850 and carried out differential and fast Fourier transform analysis of the curve. And the results concluded that blasting vibration with tandem shaped charging warhead mainly comes from prime charge; the attenuation law can be predicted by Sadev’s Formula. Explosion vibration frequency range is 20-150 Hz, while with the increase of distance from the blasting center, blasting vibration intensity attenuates rapidly, vibration duration increases and vibration frequency gradually reduces. Compared with general rock blasting, its attenuation rate of blasting vibration is faster with higher frequency and smaller impact on buildings, but the harm effects should not be ignored for the special application environment.