Sickle-configuration

P212121 Z = 4 D = 1.25 R = 0.069 number of intensities not reported. This analysis was to confirm a configuration derived from n.m.r. data. The pyranoid rings are slightly distorted 4Q, due to fusion to the trioxacyclooctane ring, which has an almost ideal, boat-chair conformation. The overall molecule has a convex, sickle conformation. There is an error in the atomic coordinates reported, which do not correspond to the structure given in the paper. 

The preferential -configuration of the enol esters, derived from p-dicarbonyl compounds under phase-transfer conditions, contrasts with the formation of the Z-enol esters when the reaction is carried out by classical procedures using alkali metal alkoxides. In the latter case, the U form of the intermediate enolate anion is stabilized by chelation with the alkali metal cation, thereby promoting the exclusive formation of the Z-enol ester (9) (Scheme 3.5), whereas the formation of the ion-pair with the quaternary ammonium cation allows the carbanion to adopt the thermodynamically more stable sickle or W forms, (7) and (8), which lead to the E-enol esters (10) [54],... 

Smith, W.S., Sickles, R.A., Miller, LA., and Womer, T.W., An Experimental Investigation into Solids Feeding Characteristics of a Single Piece Barrel with Integral Feed-port Design vs a Standard Two Piece Water Cooled Feedblock and Barrel Configuration, SPE ANTEC Tech. Papers, 53, 390 (2007)... 

Val 1-NAl, Lys 82-EF6, and His 143-H21) and deoxy Hb-S does not produce configuration changes which influence the aggregation of the molecules (B35). Moreover, cyanate (HN=C=0) which carbamylates amino terminal residues of proteins (R—NH—CO—NH2) is an effective inhibitor of sickling of erythrocytes in vitro and of gelling of concentrated solutions of deoxyhemoglobin S (C9). Addition of some specific hemoglobin variants, Hb-O-Arab or 02 2 (M16) and Hb-Korle Bu... 

The dimolybdates and ditungstates found with arabitol are closely related to the complex anions 14 and 21. Two dimolybdates are formed with D-arabitol ligands which adopt a sickle conformation with their eryf/tro-configured end as in 14 (O Fig. 2), this is the C4 chain from C2 to C5, in each case. The isomers differ in the coordination pattern one isomer has C2 and C4 in the /X2 mode, the other one C3 and C5 [25]. These isomers are the main species with tungsten(vi) as well, but a minor species is additionally formed in which the threo end of D-arabitol, this is Cl to C3, is used for complexation closely related to 21 [26,37]. 

P2i Z = 2 Dx = 1.384 R = 0.071 for 3,427 intensities. Absolute configuration confirms that nogalose is a derivative of 6-deoxy-L-mannose. The molecule has an open-chain shape, with a sickle carbon-chain conformation, thereby permitting formation of an intramolecular hydrogen-bond between O-l-H and 0-5-H at either end of the chain. 

Even a small change of one amino acid substituted for another can drastically alter the configuration of the protein. On the other hand, some amino acid substitutions have relatively minor effect and the protein may still be able to function nearly normally. The difference between normal red blood cells and sickle cell red blood cells is one strategically placed amino acid in hemoglobin. 

In the postulated mechanism, the introduction of an oxygen molecule or carbon monoxide molecule causes an effective increase in thickness of the heme groups, and, as shown in figure 4, destroys the complementariness in configuration of the surfaces of the molecule, and thus prevents the formation of linear aggregates, and the sickling of the cells. 

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