Synthetic studies interactions

For over 15 years we have conducted research utilizing metal atoms in low temperature spectroscopic and synthetic studies at Rice University.8 Our synthetic work was started in the late 1960s with the work of Krishnan, on lithium atom reactions with carbon monoxide, extended by Meier- in his studies of lithium atom reactions with water and ammonia and expanded over the next several years to include metal atom interactions with HF, H2O, H3N, H4C, and their hundreds of organic analogs—RF, R2O, ROH, R3N,. . . H3N, R4C, R3CH, etc. A most exciting aspect of... 

In addition to the chain length, the hydrocarbon chain unsaturation also plays a very important role. This is clearly shown by the data on cationic PCs, which demonstrate drastic transfection increase with increase of the number of double bonds per lipid from 0 to 2 (Fig. 13a). Studies on double chained pyridinium compounds SAINT (Synthetic Amphiphile INTeraction) (Fig. 17, inset) have shown that, while elongation of the saturated alkyl chains from 06 0/06 0 to 08 0/08 0 resulted in a reduction by a factor of about two in the transfection efficiency, introduction of double bonds reversed this effect and resulted in very strong increase of the transfection efficiency (Fig. 17). When substituting only one of the saturated 08 0 alkyl chains for unsaturated 08 1 chain, the transfection efficiency increased by an order of magnitude, while the diunsaturated compound,... 

Two other types of specific side-chain interactions have been proposed to stabilize the a helix formed by C-peptide (Shoemaker et al., 1987b). A salt bridge between Glu-2 and Arg-10 has been detected in the crystal structure of ribonuclease A (Wlodawer and Sjolin, 1983) as well as in C-peptide in aqueous solution (Rico et al., 1986). This salt bridge also fixes the N-terminal boundary of the helix between Glu-2 and Thr-3. It is not sterically possible to make this ion pair if Glu-2 is part of the helix. Synthetic studies in which either Glu-2 or Arg-10 is replaced by Ala have provided support for the importance of this interaction in stabilizing the a-... 

Larger oligopeptide hormones are also stabilized by such interactions. A nuclear magnetic resonance spectroscopic study of somatostatin by Hirschmann and co-workers (Arison et al., 1981) revealed that the side chains of phenylalanine-6 and phenylalanine-11 make the edge-to-face aromatic-aromatic interaction. Synthetic studies have shown that elimination of one or both of the aromatic groups at positions 6 and 11 abolishes biological activity. However, there is one notable exception. When... 

Synthetic studies on cyclic guanidine natural products for the elucidation of their controlling mechanism of protein-protein interaction 06Y539. 

Kwak (and co-workers) (10) were the first to employ the electrode method to study interactions involving ionic polymer systems—in their case a series of polyanions of both synthetic and natural origin, and the cationic surfactants, alkyltrimethylammonium and alkyl-pyridinium halides (69,70). ... 

This review presents a perspective of the important structural and synthetic studies reported in the year 2000. As with the previous few years reports, the strict definition of an organometallic compound as one containing at least one C-metal interaction or bond has been used in this survey (with some exceptions, where appropriate). Although based on an extensive literature search, the text is not intended to be fully comprehensive but to highlight major areas of current and potential future interest. The review has been written as near as is possible as continuous text, focusing on the most important discoveries made and any interrelations between them. In order to facilitate rapid access to a particular subject heading, individual topic headings have been placed in bold script in the text. 

In synthetic studies of gleosporone, an autoinhibitor of spore germination, Schreiber reported a highly stereoselective Ferrier-type reaction of cyclic enol ether 77 (Scheme 1.10) [29]. It is likely that minimization of A, 3 interactions in the cyclic oxonium intermediate (cf. 79) is the controlling feature in this diastereoselective process. 

Two nucleation processes important to many people (including some surface scientists ) occur in the formation of gallstones in human bile and kidney stones in urine. Cholesterol crystallization in bile causes the formation of gallstones. Cryotransmission microscopy (Chapter VIII) studies of human bile reveal vesicles, micelles, and potential early crystallites indicating that the cholesterol crystallization in bile is not cooperative and the true nucleation time may be much shorter than that found by standard clinical analysis by light microscopy [75]. Kidney stones often form from crystals of calcium oxalates in urine. Inhibitors can prevent nucleation and influence the solid phase and intercrystallite interactions [76, 77]. Citrate, for example, is an important physiological inhibitor to the formation of calcium renal stones. Electrokinetic studies (see Section V-6) have shown the effect of various inhibitors on the surface potential and colloidal stability of micrometer-sized dispersions of calcium oxalate crystals formed in synthetic urine [78, 79]. 

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