Electron Spin Resonance of Adenosine Triphosphate
IT has been suggested that in adenosine triphosphate (ATP) the phosphate chain and the adenine are linked by the pentose, so that the two terminal phosphates touch the two nitrogen atoms at positions 6 and 7 in the adenine ring1; and that, since triphosphate compounds might be electron acceptors and adenine is a good electron donor, the adenine group might donate an electron to the triphosphate group2. I. Isenberg and A. Szent-Györgyi2 obtained an electron spin resonance signal from ATP (di-sodium salt) which they attributed to internal charge transfer between the adenine and the triphosphate. They also suggested that there was a possibility that the signal could be due to a transition metal impurity in the form of a transition metal – ATP complex. In view of the great importance of ATP in living processes, we have re-examined the electron spin resonance of this compound to decide between these possibilities.
A Study of Manganous Complexes by Paramagnetic Resonance Absorption
THE paramagnetic resonance absorption of unstable metal complexes in aqueous solution has been explored and has been applied to the measurement of dissociation constants of such complexes. The method has the obvious limitation, in common with other magnetic methods, that direct measurements are confined to those ions and molecules which are paramagnetic. On the other hand, the method, in common with other spectroscopic methods, has the advantage that it can measure directly and rapidly the concentration of the free metal ion in solution without disturbing any pre-existing equilibrium state.
Genetics of speciation in the Aedes (Stegomyia) scutellaris group (Diptera: Culicidae) V. Chromosomal relationships among five species
A comparison was made of karyotypes of 5 species in the Aedes scutellaris group and their hybrids. All species had 3 distinct pairs of metacentric chromosomes (2n=6). These were of similar lengths in Ae: malayensis and Ae. alcasidi, and in Ae. polynesiensis and Ae. pseudoscutellaris. However, chromosome 1 in Ae. polynesiensis and Ae. kesseli, and chromosome 2 in Ae. pseudoscutellaris and Ae. kesseli were of unequal lengths. Meiotic analyses revealed that chromosome asynapsis was frequently seen in species hybrids. There was a significant variation in chiasma frequencies between species and their hybrids. However, the mean chiasma frequency was species specific. In addition, the mean chiasma frequency of species hybrids and the extent of chromosomal asynapsis provided a measure of genetic homology between species. Based on the assumption that a dicentric bridge and an acentric fragment were due to a single crossover within a paracentric inversion loop the following conclusions are made. Ae. malayensis and Ae. alcasidi are polymorphic for one paracentric inversion in chromosome 1. Ae. polynesiensis and Ae. pseudoscutellaris, and Ae. pseudoscutellaris and Ae. kesseli are fixed for one paracentric inversion in chromosome 2. Similarly, Ae. polynesiensis and Ae. kesseli are fixed for one paracentric inversion in chromosome 1. These chromosomal differences between species are discussed with respect to hybrid fertility data reported earlier.