Infrared Studies on Complexes of Mg⁺⁺ with Adenosine Phosphates¹

Abstract

affect an electrostatic repulsion dependent upon the charge density of the complexing anion. In order to conform to the observation that increasing the ionic strength of the same salt does not affect the energy of activation, we would have to postulate that these sites are fully saturated at low salt concentrations.The following scheme is the summary of the proposed mechanism of collagen formation and its reversal T -*• T* Collagen where T is tropocollagen, ', the inactive form and T*, the proposed intermediate that is being formed during the lag period. ' is formed when active sites on tropocollagen are blocked by anions, cations or by such agents as urea.Conditions which enhance hydrogen bonding favor the formation of collagen, while those which rupture hydrogen bonds reverse the equilibrium. The equilibrium rate will be influenced by pH, type and ionic strength of the salt present, concentration of the protein and temperature. Thus, when the collagen solution is removed from the presence of the fiber and conditions are adjusted to favor collagen formation, the system will remain poised unless conditions also favor a reasonable rate of reaction.In writing this paper, we have avoided the use of such terms as neutral-soluble or acid-soluble collagen. The impressions gained from this work have cast considerable doubt in our minds as to whether such differences really exist. It must be realized that when HO Ac solutions of collagen are adjusted to values above pH 7, the optimum pH of fiber formation is being approached. If the other variables are such as to favor coagulation, fiber formation will occur.If not, a collagen solution which is soluble in neutral or alkaline solutions will be obtained. We have found that after coagulation, the fibers can be redissolved in HO Ac, the collagen reneutralized, and fibril formation repeated as before.

A Raman study of the binding of Fe(III) to ATP and AMP

“…According to eqn. (3), the depolarization ratio should also decrease, as p is a monotonously increasing function of y2 for constant a. On the other hand, the value of a is a measure of the 'average' polarizability [15] and will probably change much less and remain essentially unchanged since no additional electron is introduced or removed from the adenine moiety.…”

“…The interactions of bivalent metal ions, Mg2+, Ca2+, Zn2+, Mn2+, Cu2+, Co2+, Hg2+, with adenine phosphates have been studied by various spectroscopic techniques, including resonance Raman spectroscopy [3][4][5][6][7][8][9][10][11]. Most Raman studies on metal-adenosine phosphate interaction have concentrated on the phosphate moiety which is known to interact strongly with all metal cations studied.…”

The bioconjugation mechanism of purine cross-linkers affects microstructure and cell response to ultra rapidly gelling purine–chitosan sponges

“…As expected, ADP and GDP yielded the same major peaks. Both molecules showed characteristic absorption peaks at 903 cm -1 due to the pyrophosphate (P-O-P) groups in purine, at 1100 cm -1 for the P-O stretching vibration and at 1222 cm -1 for the P=O group [37][38][39] . The peaks of ADP and GDP above 1300 cm -1 were mainly assigned to the adenine, guanine and ribose part of the nucleotides 40 .…”

Magnesium and Calcium in Isolated Cell Nuclei

“…Such evidence is supported by experiments showing complex formation between A D P and A T P and a divalent cation (29). At this point a reference should be made to non-aqueous nuclei.…”