Side-chain structures

Ammalahti, E. Brunow, G. Bardet, M. Robert, D. Kilpelainen, I. Identification of side-chain structures in a poplar lignin using three-dimensional HMQC-HOHAHA NMR spectroscopy. J. Agric. Food Chem. 1998, 46, 5113-5117. 

Akiyama, T. Sugimoto, T. Matsumoto, Y. Meshitsuka, G. Erythrolthreo ratio of [i-O-4 structures as an important structural characteristic of lignin. I improvement of ozonation method for the quantitative analysis of lignin side-chain structure. J. Wood Sci. 2002, 48, 210-215. 

Ejlertsson J, Alnervik M, Jonsson S, Svensson BH (1997) Influence of water solubility, side-chain structure on the degradation of phthalic acid esters under methanogenic conditions. Environ Sci Technol 31 2761-2764... 

Figure 1.2 Individual amino acids consist of a primary (a) amine, a carboxylic acid group, and a unique side-chain structure (R). At physiological pH, the amine is protonated and bears a positive charge, while the carboxylate is ionized and possesses a negative charge.

Figure 1.18 Reaction of proline, arginine, and lysine residues with hydroxyl radical results in oxidation of side-chain structures that form carbonyls. Both arginine and proline oxidation result in the same product.

Table 2.2 The 20 commonly occurring amino acids. They may be subdivided into five groups on the basis of side-chain structure. Their three- and one-letter abbreviations are also listed (one-letter abbreviations are generally used only when compiling extended seguence data, mainly to minimize writing space and effort). In addition to their individual molecular masses, the percentage occurrence of each amino acid in an average protein is also presented. These data were generated from seguence analysis of over 1000 different proteins...

Except for the side chain structure of the alcohol moiety, there is a great difference between natural pyrethrins and dxT/ram-allethrin in that the former consists of the mixture of pyrethrins I and II (5-10, Fig. 5), whereas the latter does not contain pyrethrin II homologs. 

The D. pulchra furanone compounds generally consist of a furan ring structure with a substituted alkyl chain at the C-3 position and a bromine substitution at the C-4 position (Fig. 5). The substituent at the C-5 position may vary in terms of side chain structure. The natural furanones are halogenated at various positions by bromine, iodine, or chlorine [128]. D. pulchra produces at least 30 different halogenated furanones which are stored in specialized vesicles and are released at the surface of the thallus at concentrations ranging from 1 to 100 ng/cm2 [132]. Field experiments have demonstrated that the surface concentration of furanones is inversely correlated with the degree of colonization by marine bacteria [133]. 

The rate of acid-catalyzed degradation of the penicillins also depends largely on the nature of their acylamido side chain. Structure-activity-relationship studies undertaken for the rational design of orally active penicillins have shown that the stability in gastric juice increases with the sum of Taft s inductive substituent constants (of values) of the 6-amino side chain [95]. 

In addition, the idea of the terpenoid side chain of 10 essentially assisting in anchoring the coenzyme in the cytoplasmic membrane without having any impact on the redox potential was to be explored. To this end, a number of phenazine ethers 44a-g were synthesized by Williamson ether synthesis and then investigated by electrochemical methods. And indeed, we were able to identify a good match between the redox potentials of the various phenazine ethers, which turned out to be independent of the side chain structure. 

The synthesis just described is the most direct, general three-component synthesis of PGs. Because researchers are attracted to its simplicity, a number of related syntheses have been accomplished (14). Some syntheses are achieved by using cyclopentenones with full or partial side-chain structures. 

Observation of an abnormally large shift in the position of fluorescent emission of pyridoxal phosphate (PLP) in glycogen phosphorylase answered an interesting chemical question.187188 A 330 nm (30,300 cm ) absorption band could be interpreted either as arising from an adduct of some enzyme functional group with the Schiff base of PLP and a lysine side chain (structure A) or as a nonionic tautomer of a Schiff base in a hydrophobic environment (structure B, Eq. 23-24). For structure A, the fluorescent emission would be expected at a position similar to that of pyridoxamine. On the other hand, Schiff bases of the... 

The major pathways for the fragmentation of kojic acid (81,5-hydroxy-2-hydroxymethyl-pyran-4-one), are shown in Scheme 14 support for each route was provided by the appearance of metastable ion peaks (67MI22203). An RDA cleavage followed by loss of a CH2OH radical produces ion (81a), m/e 69, the structure of which was substantiated by deuteration experiments. The ion at m/e 97 arises by extrusion of CO from the molecular ion and loss of HO- from the side chain structures (81b) and (81c) were proposed. Decomposition of [M]t occurs to give ethylene and an HC=0 fragment. The initial stage involves loss of a -CHO radical from the hydroxymethyl substituent, a process which has... 

In normal-phase HPLC on a silica column, separation is based on the number and position of methyl substituents on the chromanol ring. In reversed-phase HPLC on a Cl8 column, separation is based on the structure of the side chain and the number of methyl substituents. It is therefore difficult to completely separate [3-and y-tocopherol and (3- and y-tocotrienols by reversed-phase HPLC, because both have the same side-chain structure and number of methyl substituents on the chromanol ring. Only six peaks are usually found in the reversed-phase HPLC method. Thus, reversed-phase HPLC is recommended for samples from animal tissues, which contain little or no P and y vitamers. 

A variety of alkyl halides can be employed as an electrophile in this alkylation, as summarized in Table 5.8 (entries 1-5). The efficiency of the transmission of stereochemical information was not affected by the side-chain structure of the pre-existing amino acid residues, as demonstrated in the phase-transfer benzylation... 

Slotte JP, Jungner M, Vilcheze C, Bittman R (1994) Effect of sterol side-chain structure on sterol-phosphatidylcholine interactions in monolayers and small unilamellar vesicles. Biochim Biophys Acta Biomemhr 1190 435 143... 

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