scholarly journals THE EFFECT OF ISOELECTRIC AMINO ACIDS ON THE pH+ OF A PHOSPHATE BUFFER SOLUTION

1930 ◽  
Vol 13 (5) ◽  
pp. 509-527 ◽  
Author(s):  
Henry Borsook ◽  
Douglas A. MacFadyen
Keyword(s):  
Amino Acids ◽  
Dissociation Constants ◽  
Pure Water ◽  
Phosphate Buffer Solution ◽  
Dielectric Constants ◽  
Buffer Solution ◽  
Strong Electrolytes ◽  
Classical Conception ◽  
Zwitter Ion ◽  
Acetic Acids

The relative merits of the classical conception and of the Zwitter Ion conception of the dissociation of amphoteric electrolytes are discussed, and the following data are presented which confirm the Zwitter Ion hypothesis of Bjerrum, and which are not in accord with the classical view. 1. Amino acids in the isoelectric form resemble strong electrolytes in that they contribute to the ionic strength of the solution. 2. The dielectric constants of aqueous solutions of amino acids, like those of solutions of strong electrolytes greater than 0.02 normal, are considerably greater than that of pure water. 3. The magnitude of the dissociation constants of substituted acetic acids and of glycine, are more easily accounted for with the Zwitter Ion than with the classical conception.

scholarly journals Performance of Polyester-Based Electrospun Scaffolds under In Vitro Hydrolytic Conditions: From Short-Term to Long-Term Applications

Nanomaterials ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 786 ◽  
Author(s):  
Oscar Gil-Castell ◽  
José David Badia ◽  
Jordi Bou ◽  
Amparo Ribes-Greus
Keyword(s):  
Molar Mass ◽  
Pure Water ◽  
Phosphate Buffer Solution ◽  
Short Term ◽  
Buffer Solution ◽  
Electrospun Scaffolds ◽  
The Stability ◽  
Short Time

The evaluation of the performance of polyesters under in vitro physiologic conditions is essential to design scaffolds with an adequate lifespan for a given application. In this line, the degradation-durability patterns of poly(lactide-co-glycolide) (PLGA), polydioxanone (PDO), polycaprolactone (PCL) and polyhydroxybutyrate (PHB) scaffolds were monitored and compared giving, as a result, a basis for the specific design of scaffolds from short-term to long-term applications. For this purpose, they were immersed in ultra-pure water and phosphate buffer solution (PBS) at 37 °C. The scaffolds for short-time applications were PLGA and PDO, in which the molar mass diminished down to 20% in a 20–30 days lifespan. While PDO developed crystallinity that prevented the geometry of the fibres, those of PLGA coalesced and collapsed. The scaffolds for long-term applications were PCL and PHB, in which the molar mass followed a progressive decrease, reaching values of 10% for PCL and almost 50% for PHB after 650 days of immersion. This resistant pattern was mainly ascribed to the stability of the crystalline domains of the fibres, in which the diameters remained almost unaffected. From the perspective of an adequate balance between the durability and degradation, this study may serve technologists as a reference point to design polyester-based scaffolds for biomedical applications.

scholarly journals Validation of a Simple HPLC-Based Method for Lysine Quantification for Ruminant Nutrition

Molecules ◽  
2021 ◽  
Vol 26 (14) ◽  
pp. 4173
Author(s):  
João Albuquerque ◽  
Susana Casal ◽  
Rebeca Cruz ◽  
Ingrid Van Dorpe ◽  
Margarida Rosa Garcez Maia ◽  
...  
Keyword(s):  
Amino Acids ◽  
High Performance ◽  
Phosphate Buffer Solution ◽  
Reversed Phase ◽  
Ruminant Nutrition ◽  
Buffer Solution ◽  
Chromatography Method ◽  
Nutrition Supplementation ◽  
The Matrix ◽  
Liquid Chromatography Method

Robust and selective quantification methods are required to better analyze feed supplementation effectiveness with specific amino acids. In this work, a reversed-phase high-performance liquid chromatography method with fluorescence detection is proposed and validated for lysine quantification, one of the most limiting amino acids in ruminant nutrition and essential towards milk production. To assess and widen method applicability, different matrices were considered: namely Li2CO3 buffer (the chosen standard reaction buffer), phosphate buffer solution (to mimic media in cellular studies), and rumen inoculum. The method was validated for all three matrices and found to be selective, accurate (92% ± 2%), and precise at both the inter- and intra-day levels in concentrations up to 225 µM, with detection and quantification limits lower than 1.24 and 4.14 µM, respectively. Sample stability was evaluated when stored at room temperature, 4 °C, and −20 °C, showing consistency for up to 48 h regardless of the matrix. Finally, the developed method was applied in the quantification of lysine on real samples. The results presented indicate that the proposed method can be applied towards free lysine quantification in ruminant feeding studies and potentially be of great benefit to dairy cow nutrition supplementation and optimization.

scholarly journals ON GUAIACOL SOLUTIONS

1934 ◽  
Vol 17 (4) ◽  
pp. 563-576 ◽  
Author(s):  
Theodore Shedlovsky ◽  
Herbert H. Uhlig
Keyword(s):  
Electrical Conductivity ◽  
Partition Coefficients ◽  
Dissociation Constants ◽  
Dielectric Constants ◽  
Weak Electrolytes ◽  
Strong Electrolytes ◽  
Theoretical Considerations ◽  
Sodium And Potassium

1. Measurements are reported on the distribution of sodium and potassium guaiacolates between guaiacol and water at 25°C. 2. The variation of the partition coefficients with the concentration is explained with the aid of the Debye-Hückel interionic attraction theory and the assumption that the salts are strong electrolytes in water and weak electrolytes in guaiacol. 3. The dissociation constants of sodium and potassium guaiacolates in guaiacol previously computed from electrical conductivity determinations are shown to be in agreement with the corresponding values obtained from the distribution measurements. 4. From theoretical considerations an equation is derived with which it is possible to predict the magnitude of the limiting partition coefficients from the dielectric constants of the solvents, the size of the solute ions, and the temperature.

scholarly journals The effect of aldehyde fixation on selected substrates for energy metabolism and amino acids in mouse brain.

1978 ◽  
Vol 26 (6) ◽  
pp. 423-433 ◽  
Author(s):  
K A Conger ◽  
J H Garcia ◽  
A S Lossinsky ◽  
F C Kauffman
Keyword(s):  
Amino Acids ◽  
Initial Period ◽  
Operative Procedure ◽  
Light And Electron Microscopy ◽  
Phosphate Buffer Solution ◽  
Fold Increase ◽  
Buffer Solution ◽  
Aldehyde Fixation ◽  
Excellent Preservation

The effect of aldehyde fixation on concentrations of low molecular weight constituents was determined by comparing amounts of selected intermediates in brains of mice exposed to aldehyde fixative solutions with those perfused with phosphate buffer solution alone. Aldehyde perfusion resulted in excellent preservation of cerebral cortex ultrastructure in the presence of dramatic declines in adenosine triphosphate, phosphocreatine, glucose and glucose-6-phosphate that occureed before exposure of the tissue to aldehyde fixatives. Decreases in hexose were accompanied by approximately a 4-fold increase in lactate and a 2-fold increase in pyruvate. Glycogen levels decreased by about 60% during the initial operative procedure but remained constant after aldehyde fixation. Glycogen content declined approximately 90% in tissues that were not treated with aldehyde. Concentrations of aspartate and glutamate changed only slightly during the initial period (1-5 min) and remained constant for at least 90 min in cerebral cortices fixed with aldehydes. Alanine levels increased in both fixed and unfixed tissue; however, this increase was much smaller in tissues exposed promptly to aldehydes. Total ninhydrin-positive material in perchloric acid extracts of brain decreased in mice exposed to aldehyde solutions but increased in tissues that were not. These results indicated that several amino acids may be measured reliably in tissues preserved for light and electron microscopy. In addition, determination of glutamate: alanine ratios in tissues perfused with aldehydes may provide an indication of the timing of fixation.

Detection of Hepatitis a Virus in Drinking Water by Enzyme -Immunoassay Using Ultracentrifugation for Virus Concentration

1985 ◽  
Vol 17 (10) ◽  
pp. 39-41 ◽  
Author(s):  
A. Schnattinger
Keyword(s):  
Membrane Filtration ◽  
Hepatitis A ◽  
Hepatitis A Virus ◽  
Solid Phase ◽  
Phosphate Buffer Solution ◽  
Enzyme Linked Immunosorbent Assay ◽  
Virus Concentration ◽  
Buffer Solution ◽  
Solution Ph ◽  
Two Stage

Ten litres of tapwater were seeded with 200 µl (8×108 HAV particles) of a commercial (Organon Teknika) suspension of hepatitis A virus. Following WALTER and RÜDIGER (1981), the contaminated tapwater was treated with a two-stage technique for concentration of viruses from solutions with low virus titers. The two-stage technique consists of aluminium hydroxideflocculation (200 mg/l Al2(SO4)3. 18 H2O, pH 5,4-5,6) as first stage, the second stage of a lysis of aluminium hydroxidegel with citric acid/sodium citrate-buffer (pH 4,7; 1 ml/l sample), separation of viruses from the lysate by ultracentrifugation and suspension in 1 ml phosphate buffer solution (pH 7,2). A commercial solid phase enzyme-linked immunosorbent assay (ELISA) was used for the detection of HAV. HAV was detecterl in the 10.000:1 concentrates, but not in the seeded 101 samples. Approximately 4×108 of the inoculated 8×108 HAV particles were found in the 1 ml concentrates. The efficiency of detection is about 50%, the virus concentration 5000-fold. Although the percentage loss of HAV in comparison with concentration by means of membrane filtration is similar, the ultracentrifugation method yields a larger sample/concentrate ratio, so that smaller amounts of HAV can be detected more efficiently because of the smaller end-volume.

Non-enzymatic determination of purine nucleotides using a carbon dot modified glassy carbon electrode

2019 ◽  
Vol 11 (30) ◽  
pp. 3866-3873 ◽  
Author(s):  
R. Karthikeyan ◽  
D. James Nelson ◽  
S. Abraham John
Keyword(s):  
Glassy Carbon ◽  
Low Cost ◽  
Phosphate Buffer Solution ◽  
Purine Nucleotides ◽  
Buffer Solution ◽  
Solution Ph ◽  
Carbon Dot ◽  
Enzymatic Determination ◽  
Sensitive Determination

Selective and sensitive determination of one of the purine nucleotides, inosine (INO) using a low cost carbon dot (CD) modified glassy carbon (GC) electrode in 0.2 M phosphate buffer solution (pH 7.2) was demonstrated in this paper.

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