ChemInform Abstract: SYNTHESIS OF A NEW AMINO ACID BASE CROSS-LINKER FOR PREPARATION OF SUBSTRATE SELECTIVE ACRYLIC POLYMERS

1985 ◽  
Vol 16 (49) ◽  
Author(s):  
L. ANDERSSON ◽  
B. EKBERG ◽  
K. MOSBACH
Keyword(s):  
Amino Acid ◽  
Acid Base ◽  
Acrylic Polymers ◽  
Cross Linker

Synthesis of a new amino acid based cross-linker for preparation of substrate selective acrylic polymers

1985 ◽  
Vol 26 (30) ◽  
pp. 3623-3624 ◽  
Author(s):  
Lars Andersson ◽  
Björn Ekberg ◽  
Klaus Mosbach
Keyword(s):  
Amino Acid ◽  
Acrylic Polymers ◽  
Cross Linker

scholarly journals Testing the Effectiveness of Protocols for Removal of Common Conservation Treatments for Radiocarbon Dating

Radiocarbon ◽  
2017 ◽  
Vol 60 (1) ◽  
pp. 35-50 ◽  
Author(s):  
Fiona Brock ◽  
Michael Dee ◽  
Andrew Hughes ◽  
Christophe Snoeck ◽  
Richard Staff ◽  
...  
Keyword(s):  
Organic Solvent ◽  
Vinyl Acetate ◽  
Radiocarbon Dating ◽  
Cellulose Nitrate ◽  
Acid Base ◽  
Acrylic Polymers ◽  
Archaeological Wood ◽  
Conservation Treatment ◽  
Chemical Pretreatments ◽  
Selection Of

AbstractTo achieve a reliable radiocarbon (14C) date for an object, any contamination that may be of a different age must be removed prior to dating. Samples that have been conserved with treatments such as adhesives, varnishes or consolidants can pose a particular challenge to 14C dating. At the Oxford Radiocarbon Accelerator Unit (ORAU), common examples of such substances encountered include shellac, the acrylic polymers Paraloid B-67 and B-72, and vinyl acetate-derived polymers (e.g. PVA). Here, a non-carbon-containing absorbent substrate called Chromosorb® was deliberately contaminated with a range of varieties or brands of these conservation treatments, as well as two cellulose nitrate lacquers. A selection of chemical pretreatments was tested for their efficiency at removing them. While the varieties of shellac and Paraloid tested were completely removed with some treatments (water/methanol and acetone/methanol/chloroform sequential washes, respectively), no method was found that was capable of completely removing any of the vinyl acetate-derived materials or the cellulose nitrate lacquers. While Chromosorb is not an exact analog of archaeological wood or bone, for example, this study suggests that it may be possible to remove aged shellac and Paraloid from archaeological specimens with standard organic solvent-acid-base-acid pretreatments, but it may be significantly more difficult to remove vinyl acetate-derived polymers and cellulose nitrate lacquers sufficiently to provide reliable 14C dates. The four categories of conservation treatment studied demonstrate characteristic FTIR spectra, while highlighting subtle chemical and molecular differences between different varieties of shellac, Paraloid and cellulose nitrate lacquers, and significant differences between the vinyl acetate derivatives.

Changes in metabolic rate and N excretion in the marine invertebrateSipunculus nudusunder conditions of environmental hypercapnia

2002 ◽  
Vol 205 (8) ◽  
pp. 1153-1160 ◽  
Author(s):  
M. Langenbuch ◽  
H. O. Pörtner
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Metabolic Rate ◽  
Intracellular Ph ◽  
Energy Demand ◽  
Control Level ◽  
Ammonia Excretion ◽  
Amino Acid Catabolism ◽  
Acid Base ◽  
Selection Of

SUMMARYIncreased CO2 partial pressures (hypercapnia) as well as hypoxia are natural features of marine environments like the intertidal zone. Nevertheless little is known about the specific effects of CO2 on metabolism, except for the well-described effects on acid—base variables and regulation. Accordingly, the sediment-dwelling worm Sipunculus nudus was used as an experimental model to investigate the correlation of acid—base-induced metabolic depression and protein/amino acid catabolism, by determining the rates of oxygen consumption, ammonia excretion and O/N ratios in non-perfused preparations of body wall musculature at various levels of extra- and intracellular pH, PCO2 and [HCO3-]. A decrease in extracellular pH from control level (7.9) to 6.7 caused a reduction in aerobic metabolic rate of both normocapnic and hypercapnic tissues by 40-45 %. O/N ratios of 4.0-4.5 under control conditions indicate that amino acid catabolism meets the largest fraction of aerobic energy demand. A significant 10-15 % drop in ammonia excretion, a simultaneous reduction of O/N ratios and a transient accumulation of intracellular bicarbonate during transition to extreme acidosis suggest a reduction in net amino acid catabolism and a shift in the selection of amino acids used,favouring monoamino dicarboxylic acids and their amines (asparagine,glutamine, aspartic and glutamic acids). A drop in intracellular pH was identified as mediating this effect. In conclusion, the present data provide evidence for a regulatory role of intracellular pH in the selection of amino acids used by catabolism.

Acute acidosis inhibits liver amino acid transport: no primary role for the urea cycle in acid-base balance

1994 ◽  
Vol 267 (6) ◽  
pp. F1015-F1020 ◽  
Author(s):  
L. Boon ◽  
P. J. Blommaart ◽  
A. J. Meijer ◽  
W. H. Lamers ◽  
A. C. Schoolwerth
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Hepatic Vein ◽  
Amino Acid Transport ◽  
Amino Acid Uptake ◽  
Acid Uptake ◽  
Primary Role ◽  
Urea Synthesis ◽  
Acid Transport ◽  
Acid Base

To examine further the role of the liver in acid-base homeostasis, we studied hepatic amino acid uptake and urea synthesis in rats in vivo during acute acidosis and alkalosis, induced by infusion of 1.8 mmol of HCl or NaHCO3 over 3 h. Amino acids and NH4+ were measured in portal vein, hepatic vein, and aortic plasma, and arteriovenous differences of amino acids and urinary urea and NH4+ excretion were measured. In acidosis, urinary urea excretion was reduced 36% (P < 0.01), whereas urinary NH4+ excretion increased ninefold (P < 0.01), but the sum of urea and NH4+ excretion was unchanged. Total hepatic amino acid uptake, as determined from arteriovenous differences, was decreased by 63% (P < 0.01) in acidosis, with the major effect being noted with alanine and glycine. Only glutamine was released in both acidosis and alkalosis but was not significantly different in the two conditions. Since intracellular concentrations of readily transportable amino acids were not different at low pH despite accelerated protein degradation, these results indicate that hepatic amino acid transport was inhibited markedly and sufficiently to explain the observed decrease in urea synthesis. Total hepatic vein amino acid content was greater in acidosis than alkalosis (P < 0.01). Directly or indirectly, by conversion to glutamine elsewhere, these increased amino acids were degraded in kidney and accounted for the ninefold increase in urinary NH4+ excretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain amino acid concentrations during diving and acid-base stress in turtles

1985 ◽  
Vol 58 (6) ◽  
pp. 1751-1754 ◽  
Author(s):  
B. M. Hitzig ◽  
M. P. Kneussl ◽  
V. Shih ◽  
R. D. Brandstetter ◽  
H. Kazemi
Keyword(s):  
Amino Acid ◽  
Aminobutyric Acid ◽  
Breath Hold ◽  
Gamma Aminobutyric Acid ◽  
Amino Acid Neurotransmitters ◽  
Acid Base ◽  
Ventilatory Drive ◽  
Amino Acid Concentrations ◽  
Brain Amino Acid

To assess the role of brain amino acid neurotransmitters in the breath hold of diving animals, concentrations of free amino acids present in the brains of turtles immediately after 2 h of apneic diving (at 20 degrees C) were measured. Additionally, the same measurements were performed on four other groups of animals subjected to 2 h of hypercapnia (8% CO2 in air), anoxia (N2 breathing), anoxia plus hypercapnia (8% CO2–92% N2), or air breathing (control). Significant changes in the concentrations of the inhibitory amino acid neurotransmitters known to affect respiration [gamma-aminobutyric acid (GABA) and taurine] were seen. GABA increased significantly in those animals subjected to anoxia, whereas taurine decreased significantly in the diving animals and increased significantly in those subjected to anoxia plus hypercapnia. These results suggest that the attenuated central ventilatory drive during diving in these animals may be related to alterations in brain concentrations of GABA and taurine.

scholarly journals Towards Novel Amino Acid-Base Contacts in Gene Regulatory Proteins: AraR – A Case Study

PLoS ONE ◽  
2014 ◽  
Vol 9 (11) ◽  
pp. e111802 ◽  
Author(s):  
Isabel Lopes Correia ◽  
Irina Saraiva Franco ◽  
Isabel de Sá-Nogueira
Keyword(s):  
Amino Acid ◽  
Regulatory Proteins ◽  
Acid Base ◽  
Gene Regulatory
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