Molecular relations from

Polyacrylic acid (pAA) homopolymers and related copolymers have become a commercially important class of water-soluble polymers. Acrylic acid polymers can range in molecular mass from less than 1000 Da to greater than 1,000,000 Da. A representative set of analysis conditions is... 

One is purely formal, it concerns the departure from symmetry of an approximate solution of the Schrodinger equation for the electrons (ie within the Bom-Oppenheimer approximation). The most famous case is the symmetry-breaking of the solutions of the Hartree-Fock equations [1-4]. The other symmetry-breaking concerns the appearance of non symmetrical conformations of minimum potential energy. This phenomenon of deviation of the molecular structure from symmetry is so familiar, confirmed by a huge amount of physical evidences, of which chirality (i.e. the existence of optical isomers) was the oldest one, that it is well accepted. However, there are many problems where the Hartree-Fock symmetry breaking of the wave function for a symmetrical nuclear conformation and the deformation of the nuclear skeleton are internally related, obeying the same laws. And it is one purpose of the present review to stress on that internal link. 

The crystallographic structure of rubredoxin from Clostridium pasteurianum at 2.5 A, a resolution sufficient to reveal the sequence of several of the bulky amino acid side chains, shows the iron coordinated to two pairs of cysteine residues located rather near the termini of the polypeptide chain (Fig. 1). A related rubredoxin, with a three times larger molecular weight, from Pseudomonas oleovorans is believed to bind iron in a similar fashion. This conclusion is based on physical probes, especially electron paramagnetic resonance spectroscopy, all of which indicate that the iron is in each case situated in a highly similar environment however, the proteins display some specificity in catalytic function. 

Glucagon is a single-chain polypeptide of 29 amino acid residues and a molecular mass of 3500 Da. It is synthesized by the A-cells of the islets of Langerhans, and also by related cells found in the digestive tract. Like insulin, it is synthesized as a high molecular mass from which the mature hormone is releases by selective proteolysis. 

Complex 69 was prepared in about 60% yield with about 15% metallation and a small drop in molecular weight (from 73,000 for PMPS to 68,000 for 69), which, allowing for the increase in statistical repeat unit, indicates some degradation. Related model compounds based on the coordination of phenyl rings in phenyltrimethylsilane and 1,2-diphenyltetramethyldisilane were compared with 69. The UV absorption maxima (224 and 337 nm) were almost unchanged from those of the precursor PMPS (223 and 338 nm), which possibly reflects the low metal loading as... 

Kier, L. B. (1989) An index of molecular flexibility from kappa shape attributes. Quant. Struct.-Act. Relat. 8, 221-224. 

G. Birnbaum. Determination of molecular constants from collision-induced far-infrared spectra and related methods. In J. van Kranendonk, ed., Intermolecular Spectroscopy and Dynamical Properties of Dense Systems - Proceedings of the International School of Physics Enrico Fermi , Course LXXV, p. Ill, 1980. 

G. Birnbaum. Determination of molecular constants from collision-induced far-infra-red spectra and related methods. In [406], p. 111. 

This remarkable molecular memory was preceded by two other related examples of addressable molecular electronics from the Stoddart and Heath groups in collaboration with Hewlett-Packard scientists. First in 1999 a [2] rotaxane based system was configured into molecular AND and OR logic gates,63 then in 2000 a [2] catenane based molecular switch was reported.64 The molecular basis for the operation of this switch is the same as in 11.67, namely reorientation in response to reduction of... 

C (Table 5). These measurements can be related to the approach adopted by Duben29 who used the Hiickel MO theory to compare the reactivity of five-and six-membered ring products containing S or N. Six-membered rings, such as pyridine, produced a different distribution of 7r-molecular orbitals from that produced by five-membered rings, such as thiophene or pyrrole, in adsorbed states this factor could be the most important one when comparing the catalytic activities of different compounds. 

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