scholarly journals Tyrosine Metabolism in Blowfly Larvae at Pupation

1964 ◽  
Vol 17 (3) ◽  
pp. 803 ◽  
Author(s):  
RH Hackman KN Saxen
Keyword(s):  
Direct Evidence ◽  
Side Chain ◽  
Cross Linking ◽  
Cuticular Protein ◽  
Oxidative Deamination ◽  
Tyrosine Metabolism ◽  
Metabolic Reactions

In insects tyrosine has been regarded as participating in metabolic reactions which lead, not only to its incorporation in various proteins, but also to sclerotization of the cuticle (i.e. quinone cross-linking of cuticular protein). Three different meta-bolic pathways have been suggested, all of which lack direct evidence to support them. The suggested pathways are (i) oxidative deamination leading to the formation of o-quinones, (ii) non-specific hydroxylation and elimination of the side-chain leading to the formation of p-quinones, and (iii) conversion to N-acetyldopamine which is the phenolic precursor of the sclerotizing quinone. For a review of these theories see Pryor (1962) and Hackman (1964).

Side-Chain Cholesteric Liquid Crystalline Elastomers Derived from a Mesogenic Cross-Linking Agent

2003 ◽  
Vol 36 (24) ◽  
pp. 9060-9066 ◽  
Author(s):  
Jian-She Hu ◽  
Bao-Yan Zhang ◽  
Ying-Gang Jia ◽  
Song Chen
Keyword(s):  
Liquid Crystalline ◽  
Side Chain ◽  
Cross Linking ◽  
Cholesteric Liquid Crystalline

Anionic Cross-Linking of Polymers Having an Epoxy Group in the Side Chain with Bicyclic and Spirocyclic Bis(γ-lactone)s

1997 ◽  
Vol 30 (9) ◽  
pp. 2532-2538 ◽  
Author(s):  
Keunwo Chung ◽  
Toshikazu Takata ◽  
Takeshi Endo
Keyword(s):  
Epoxy Group ◽  
Side Chain ◽  
Cross Linking

scholarly journals Prenylquinones in Human Parasitic Protozoa: Biosynthesis, Physiological Functions, and Potential as Chemotherapeutic Targets

Molecules ◽  
2019 ◽  
Vol 24 (20) ◽  
pp. 3721
Author(s):  
Ignasi Verdaguer ◽  
Camila Zafra ◽  
Marcell Crispim ◽  
Rodrigo Sussmann ◽  
Emília Kimura ◽  
...  
Keyword(s):  
Drug Targets ◽  
Shikimate Pathway ◽  
Mitochondrial Respiratory Chain ◽  
Side Chain ◽  
Head Group ◽  
Parasitic Protozoa ◽  
Amino Acid Degradation ◽  
Phylogenetic Origin ◽  
Metabolic Reactions ◽  
Vertebrate Hosts

Human parasitic protozoa cause a large number of diseases worldwide and, for some of these diseases, there are no effective treatments to date, and drug resistance has been observed. For these reasons, the discovery of new etiological treatments is necessary. In this sense, parasitic metabolic pathways that are absent in vertebrate hosts would be interesting research candidates for the identification of new drug targets. Most likely due to the protozoa variability, uncertain phylogenetic origin, endosymbiotic events, and evolutionary pressure for adaptation to adverse environments, a surprising variety of prenylquinones can be found within these organisms. These compounds are involved in essential metabolic reactions in organisms, for example, prevention of lipoperoxidation, participation in the mitochondrial respiratory chain or as enzymatic cofactors. This review will describe several prenylquinones that have been previously characterized in human pathogenic protozoa. Among all existing prenylquinones, this review is focused on ubiquinone, menaquinone, tocopherols, chlorobiumquinone, and thermoplasmaquinone. This review will also discuss the biosynthesis of prenylquinones, starting from the isoprenic side chains to the aromatic head group precursors. The isoprenic side chain biosynthesis maybe come from mevalonate or non-mevalonate pathways as well as leucine dependent pathways for isoprenoid biosynthesis. Finally, the isoprenic chains elongation and prenylquinone aromatic precursors origins from amino acid degradation or the shikimate pathway is reviewed. The phylogenetic distribution and what is known about the biological functions of these compounds among species will be described, as will the therapeutic strategies associated with prenylquinone metabolism in protozoan parasites.

Direct evidence for the role of Maillard reaction products in protein cross-linking in milk powder during storage

2013 ◽  
Vol 31 (2) ◽  
pp. 83-91 ◽  
Author(s):  
Thao T. Le ◽  
John W. Holland ◽  
Bhesh Bhandari ◽  
Paul F. Alewood ◽  
Hilton C. Deeth
Keyword(s):  
Maillard Reaction ◽  
Direct Evidence ◽  
Milk Powder ◽  
Cross Linking ◽  
Maillard Reaction Products ◽  
Reaction Products ◽  
Protein Cross Linking

Study on Synthesis and Characterization of Unsaturated Polyester by Enzyme-Catalyzed

2013 ◽  
Vol 575-576 ◽  
pp. 67-70
Author(s):  
Fen Juan Shao ◽  
Qun Yang ◽  
Lan Ying Li ◽  
Da Nian Lu
Keyword(s):  
High Temperature ◽  
Unsaturated Polyester ◽  
Soxhlet Extraction ◽  
Side Chain ◽  
Synthesis And Characterization ◽  
Cross Linking ◽  
Cross Link ◽  
H Nmr ◽  
Ft Ir

Unsaturated polyester was prepared with adipic acid (AA), fumaric acid (FA), itaconic acid (IA) and 1, 6-hexanediol (HD) by enzyme-catalyzed polmerization. The insoluble gel fraction (Qs), as the cross-linking degree of cured unsaturated polyesters which could be self-cross-linked at high temperature through C=C in it, was got by Soxhlet Extraction. The properties were investigated by FT-IR, 1H NMR, DSC, XRD and so on. The results indicated that the C=C in unsaturated diacids reduced the acitvity of N435, which affected the polmerization. With the introduction of C=C of IA or FA, the Mn of polyester reduced. The C=C could self-cross-link under high temperature for lengthy time. The higher the temperature and the longer the time, the Qs increased. As the C=C of IA was in the side chain, it could move easily. Then Qs of poly (AA-co-IA-co-HD) was higher than ploy (AA-co-FA-co-HD). With the increased content of unsaturated diacid, Qs increased. And the biodegradation of cross-linked polyesters became worse.

Cross-Linking Behavior of Diskotic Side-Chain Polymers in Solution

2004 ◽  
Vol 37 (20) ◽  
pp. 7839-7845 ◽  
Author(s):  
Marcel W. C. P. Franse ◽  
Klaas te Nijenhuis ◽  
Jan Groenewold ◽  
Stephen J. Picken
Keyword(s):  
Side Chain ◽  
Cross Linking

Preparation of polyferrocenylsilane via thermal ROP, synthesis of polyferrocenylsilane with methacrylate side chain and its photochemical cross-linking properties

2006 ◽  
Vol 60 (11) ◽  
pp. 1416-1419 ◽  
Author(s):  
Jian-Jun Wang ◽  
Li Wang ◽  
Xue-Jie Wang ◽  
Tao Chen ◽  
Hao-Jie Yu ◽  
...  
Keyword(s):  
Side Chain ◽  
Cross Linking

Engineering oxidative stability in human hemoglobin based on the Hb providence (βK82D) mutation and genetic cross-linking

2017 ◽  
Vol 474 (24) ◽  
pp. 4171-4192 ◽  
Author(s):  
Michael Brad Strader ◽  
Rachel Bangle ◽  
Claire J. Parker Siburt ◽  
Cornelius L. Varnado ◽  
Jayashree Soman ◽  
...  
Keyword(s):  
Oxidative Degradation ◽  
Oxygen Affinity ◽  
Side Chain ◽  
Cross Linking ◽  
Critical Element ◽  
Low Oxygen ◽  
Naturally Occurring ◽  
Low Concentrations ◽  
Genetic Cross ◽  
Low Oxygen Affinity

Previous work suggested that hemoglobin (Hb) tetramer formation slows autoxidation and hemin loss and that the naturally occurring mutant, Hb Providence (HbProv; βK82D), is much more resistant to degradation by H2O2. We have examined systematically the effects of genetic cross-linking of Hb tetramers with and without the HbProv mutation on autoxidation, hemin loss, and reactions with H2O2, using native HbA and various wild-type recombinant Hbs as controls. Genetically cross-linked Hb Presbyterian (βN108K) was also examined as an example of a low oxygen affinity tetramer. Our conclusions are: (a) at low concentrations, all the cross-linked tetramers show smaller rates of autoxidation and hemin loss than HbA, which can dissociate into much less stable dimers and (b) the HbProv βK82D mutation confers more resistance to degradation by H2O2, by markedly inhibiting oxidation of the β93 cysteine side chain, particularly in cross-linked tetramers and even in the presence of the destabilizing Hb Presbyterian mutation. These results show that cross-linking and the βK82D mutation do enhance the resistance of Hb to oxidative degradation, a critical element in the design of a safe and effective oxygen therapeutic.

The Distribution of Combined Sulfur in Vulcanized Rubber and Its Bearing on the Sulfide Linkage Theory of Vulcanization

1939 ◽  
Vol 12 (2) ◽  
pp. 191-199
Author(s):  
I. Williams
Keyword(s):  
Physical Properties ◽  
Direct Evidence ◽  
Cross Linking ◽  
Direct Relation ◽  
Vulcanized Rubber ◽  
Free Sulfur

Abstract No direct evidence exists to support the sulfide linkage theory of vulcanization, which assumes that cross-linking of the molecules with sulfur would retain the elasticity and decrease the plasticity of the rubber. The following facts do not favor the sulfide linkage theory of vulcanization : (1) Vulcanized rubber can be peptized under conditions which do not appear to rupture a sulfide linkage. (2) No direct relation exists between the physical properties of vulcanized rubber and the amount of combined sulfur. (3) No direct relation exists between the ease of peptization and the physical properties of the vulcanizate. (4) Combined sulfur appears to assist the solvation of rubber. Rubber vulcanized with thiuram disulfides in the absence of free sulfur has poor physical properties but peptizes with difficulty. An increase in combined sulfur without a corresponding improvement in physical properties assists solvation. (5) Rubber having the best physical properties is also the most heterogeneous with respect to sulfur. The sulfide linkage theory would suggest that an even distribution of sulfur would produce the best physical properties. (6) Fractions of peptized vulcanizates, on evaporation of their solutions, leave insoluble vulcanized films, which shows that linkage by means of primary forces is unnecessary for producing the vulcanized condition.

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