The aqueous chemistry of tellurium: critically-selected equilibrium constants for the low-molecular-weight inorganic species

2019 ◽  
Vol 16 (4) ◽  
pp. 289 ◽  
Author(s):  
Montserrat Filella ◽  
Peter M. May
Keyword(s):  
Molecular Weight ◽  
Aqueous Solutions ◽  
Thermodynamic Data ◽  
Equilibrium Constants ◽  
Computer Programs ◽  
Experimental Investigations ◽  
Low Molecular Weight ◽  
Aqueous Chemistry ◽  
Scientific Disciplines ◽  
Inorganic Species

Environmental contextEquilibrium constants are required in many scientific disciplines such as biology, medicine, engineering, and in particular chemistry. Lack of reliable equilibrium constants for tellurium has restricted our understanding of its speciation and behaviour in the environment. This study presents a reliable set of equilibrium constants for tellurium, thereby providing a more coherent basis for future experimental investigations of the geochemistry, biochemistry and toxicology of this element. AbstractRelatively little information is available in the literature regarding the speciation and solubility of tellurium in aqueous solutions. The available thermodynamic data have been critically evaluated and entered into a thermodynamic database. The Joint Expert Speciation System suite of computer programs has been used to achieve thermodynamic consistency and provide a critically-selected set of equilibrium constants that can later be used for modelling purposes.

THE DISSOCIATION OF α- AND β-LIPOVITELLIN IN AQUEOUS SOLUTION: PART I. EFFECT OF pH, TEMPERATURE, AND OTHER FACTORS

1962 ◽  
Vol 40 (3) ◽  
pp. 363-372 ◽  
Author(s):  
R. W. Burley ◽  
W. H. Cook
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Aqueous Solutions ◽  
Thermodynamic Data ◽  
Equilibrium Constants ◽  
Effect Of Ph ◽  
Reversible Dissociation ◽  
Lipoprotein Concentration ◽  
Irreversible Aggregation ◽  
Increasing Temperature

The effect of pH, temperature, ionic strength, and lipoprotein concentration on the reversible dissociation of α- and β-lipovitellin in aqueous solutions above pH 6 has been examined by ultracentrifugal measurements. Under otherwise similar conditions α- and β-lipovitellin are 50% dissociated at pH 10.5 and 7.8, respectively. Both lipovitellins undergo an irreversible aggregation above about pH 11; β-lipovitellin is sometimes converted to a non-dissociable form upon aging. Dissociation of both lipovitellins decreases with increasing ionic strength and increasing temperature. Although the ultracentrifugal method has limitations, provisional equilibrium constants and thermodynamic data were obtained from it that are comparable with those obtained for certain protein systems.

Analysis of Bone “Collagen” Extraction Products for Radiocarbon Dating

Radiocarbon ◽  
2013 ◽  
Vol 55 (2) ◽  
pp. 445-463 ◽  
Author(s):  
F Brock ◽  
V Geoghegan ◽  
B Thomas ◽  
K Jurkschat ◽  
T F G Higham
Keyword(s):  
Amino Acids ◽  
Molecular Weight ◽  
Radiocarbon Dating ◽  
Fulvic Acids ◽  
Bone Collagen ◽  
Low Molecular Weight ◽  
Extraction Procedures ◽  
Molecular Weights ◽  
Published Evidence ◽  
Inorganic Species

Archaeological bones are now routinely dated in many radiocarbon laboratories through the extraction of “collagen.” Methods for “collagen” extraction vary, and several laboratories now apply an ultrafiltration step after gelatinization to extract the higher molecular weight (usually >10 or 30kDa) fraction for dating, thereby removing low molecular weight contaminants. Ultrafiltration has been demonstrated to result in products that are easier to handle and have more acceptable C:N ratios, and in some instances can result in significantly improved (generally older) 14C dates when compared to non-ultrafiltered products from the same bone. Although it has been suggested that ultrafiltration removes potential contaminants such as short-chain degraded collagen and other peptides and amino acids, fulvic acids, and salts, there remains little published evidence to support this. This paper presents data from a pilot study investigating the most suitable techniques with which to study the products of the routine “collagen” extraction procedures employed at the Oxford Radiocarbon Accelerator Unit (ORAU) (modified Longin followed by ultrafiltration). The preliminary data demonstrates that the final product of “collagen” extraction at ORAU appears to be an aggregate consisting of a range of proteins of different molecular weights, including collagen, as well as some other organic matter and inorganic species. Ultrafiltration is removing some, but not all, of the <30kDa fraction from the samples. Further work to investigate the nature of this aggregate and how best to improve the efficiency of “collagen” extraction procedures is discussed.

Is a cross-β-sheet structure of low molecular weight peptides necessary for the formation of fibrils and peptide hydrogels?

2018 ◽  
Vol 20 (27) ◽  
pp. 18158-18168 ◽  
Author(s):  
Niranjan V. Ilawe ◽  
Reinhard Schweitzer-Stenner ◽  
David DiGuiseppi ◽  
Bryan M. Wong
Keyword(s):  
Molecular Weight ◽  
Aqueous Solutions ◽  
Low Molecular Weight ◽  
Sheet Structure ◽  
Peptide Hydrogels ◽  
Β Sheet ◽  
Theory And Experiment

Using both theory and experiment, we identify two oligomer structures formed by tripeptides in aqueous solutions.

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