Water, Acids, Bases, and Buffers

Bhagavan, N.V.; Ha, Chung-Eun

doi:10.1016/b978-0-12-095461-2.00002-3

Cited by 6 publications

(5 citation statements)

References 17 publications

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“…Their acid-base properties (pKa) indicated the acidic behavior of diclofenac sodium and ibuprofen and the basic behavior of lidocaine and caffeine. Since the surface of the skin has a pH of approximately 5.5 and this pH increases in the inner skin strata to approximately 7 at a systemic or receptor fluid level [ 32 , 33 ], the percentages of ionized and unionized drug for all compounds following the Henderson–Hasselbach equation were calculated at these two pH values for the four drugs [ 34 , 35 ]. While diclofenac sodium and caffeine were mostly ionized in the range of the two pH values studied (negative and positive respectively), ibuprofen and lidocaine were much unionized at pH 5.5 and pH 7.0.…”

Section: Resultsmentioning

confidence: 99%

Assessment of Finite and Infinite Dose In Vitro Experiments in Transdermal Drug Delivery

et al. 2021

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Penetration, usually with finite dosing, provides data about the total active amount in the skin and permeation, being the most used methodology, usually with infinite dosing, leads to data about pharmacokinetic parameters. The main objective of this work is to assess if results from permeation, most of them at finite dose, may be equivalent to those from penetration usually at infinite dose. The transdermal behavior of four drugs with different physicochemical properties (diclofenac sodium, ibuprofen, lidocaine, and caffeine) was studied using penetration/finite and kinetic permeation/infinite dose systems using vertical Franz diffusion cells to determine the relationships between permeation and penetration profiles. Good correlation of these two in vitro assays is difficult to find; the influence of their dosage and the proportion of different ionized/unionized compounds due to the pH of the skin layers was demonstrated. Finite and infinite dose regimens have different applications in transdermal delivery. Each approach presents its own advantages and challenges. Pharmaceutical industries are not always clear about the method and the dose to use to determine transdermal drug delivery. Being aware that this study presents results for four actives with different physicochemical properties, it can be concluded that the permeation/infinite results could not be always extrapolated to those of penetration/finite. Differences in hydrophilicity and ionization of drugs can significantly influence the lack of equivalence between the two methodologies. Further investigations in this field are still needed to study the correlation of the two methodologies and the main properties of the drugs that should be taken into account.

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Section: Resultsmentioning

confidence: 99%

Assessment of Finite and Infinite Dose In Vitro Experiments in Transdermal Drug Delivery

et al. 2021

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“…The experimental reaction rate of peptide bond cleavage is much slower than that of deamidation, and the experimental activation barrier of Asn deamidation is 80–100 kJ mol –1 . , Therefore, the calculated activation barrier of peptide bond cleavage in this study is considered to be reasonable. In addition, the concentration of phosphate ions is higher than the concentration of carbonate ions in the cell and vice versa for the extracellular fluid. − Therefore, both ions are considered to be the major catalysts for the peptide bond cleavage of Asn, both inside and outside cells. The relative energy of PC was higher than that of RC in each catalyzed reaction because succinimide is an intermediate of the peptide bond cleavage of Asn.…”

Section: Resultsmentioning

confidence: 99%

Computational Analysis of the Mechanism of Nonenzymatic Peptide Bond Cleavage at the C-Terminal Side of an Asparagine Residue

et al. 2021

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The nonenzymatic peptide bond cleavage at the C-terminal side of Asn residues is a protein post-translational modification that occurs under physiological conditions. This reaction proceeds much slower than the deamidation of the Asn side chain and causes denaturation and hypofunction of proteins. The peptide bond cleavage of Asn is detected primarily in crystallins and aquaporin 0 in the eye lens. Therefore, cleavage is thought to be involved in age-related cataracts. In this study, to clarify the mechanism underlying succinimide formation for the peptide bond cleavage of the Asn residue, we performed quantum chemical calculations on the model compound Ace-Asn-Gly-Nme (Ace = acetyl and Nme = methylamino). The density functional theory with the B3LYP/6-31+G(d,p) level of theory was used to obtain optimized geometries. The results suggested that the reaction proceeds through two steps, cyclization and C-terminal fragment release, and the required proton transfers can be mediated by H 2 PO 4 − and HCO 3 − ions. The conformational change of the main chain on the N-terminal side of Asn was needed for the Cterminal fragmentation step, and a separate conformational change at the C-terminal side was required for the cyclization step. Furthermore, the calculated activation barriers of the reactions catalyzed by the H 2 PO 4 − ion (130 kJ mol −1 ) and the HCO 3 − ion (123 kJ mol −1 ) were sufficiently low for the reactions to occur under normal physiological conditions.

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“…This opposite pH evolution can be explained through calculation. In a medium buffered by carbonate, the Henderson-Hasselbalch equation allows determining the pH from carbonate concentration (Bhagavan and Ha, 2015;Davies and Moores, 2010) according to equation (4). The final concentration of CO − and HCO − 3 species can be expressed by their initial concentration together with the produced or consumed concentration of CO − and HCO − 3 , which can be expressed in nitrate equivalents according to equations (1) or (2).…”

Section: Ph Evolution During Denitrificationmentioning

confidence: 99%

Nitrate and nitrite bacterial reduction at alkaline pH and high nitrate concentrations, comparison of acetate versus dihydrogen as electron donors

Albina¹,

Durban²,

Bertron³

et al. 2021

Journal of Environmental Management

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Water, Acids, Bases, and Buffers

Cited by 6 publications

References 17 publications

Assessment of Finite and Infinite Dose In Vitro Experiments in Transdermal Drug Delivery

Assessment of Finite and Infinite Dose In Vitro Experiments in Transdermal Drug Delivery

Computational Analysis of the Mechanism of Nonenzymatic Peptide Bond Cleavage at the C-Terminal Side of an Asparagine Residue

Nitrate and nitrite bacterial reduction at alkaline pH and high nitrate concentrations, comparison of acetate versus dihydrogen as electron donors

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