The Henderson-Hasselbalch Equation: Its History and Limitations

Po, Henry N.; Senozan, N. M.

doi:10.1021/ed078p1499

Cited by 394 publications

(293 citation statements)

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“…Figure 1 shows four examples of drugs which reveal relatively simple logS-pH profiles, which can be more or less predicted by the Henderson-Hasselbalch (HH) equation [27,40,41]. Figure 2 shows three examples of molecules with logS-pH profiles that are consistent with the presence of anionic or uncharged self-associated aggregates, and one case consistent with drugbuffer interaction.…”

Section: Case Studiesmentioning

confidence: 96%

Equilibrium solubility measurement of ionizable drugs – consensus recommendations for improving data quality

et al. 2016

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Section: Case Studiesmentioning

confidence: 96%

Equilibrium solubility measurement of ionizable drugs – consensus recommendations for improving data quality

et al. 2016

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“…At the pH value of 5.5 used for real-time in situ assays, the specific activity of AtXTH31 at 1 mM XXXG-Res was 0.068 6 0.008 mol min 21 mol 21 AtXTH31, while at the optimum pH of 4.75, the specific activity was 0.28 6 0.01 mol min 21 mol 21 AtXTH31 ([S] = 1 mM), as determined in a stopped assay. It should be noted that in the in situ assays, which follow fluorescence development continuously, the resorufin aglycone will be 33% ionized at pH 5.5 (pKa = 5.8, « = 62,000 M 21 cm 21 ; Po and Senozan, 2001). This pH was selected as a compromise between maximum enzyme activity and maximum fluorescence detection sensitivity.…”

Section: Reverse Genetics Analysis Of Atxth31 and Atxth32mentioning

confidence: 99%

Group III-AXTHGenes of Arabidopsis Encode Predominant Xyloglucan Endohydrolases That Are Dispensable for Normal Growth

et al. 2012

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The molecular basis of primary wall extension endures as one of the central enigmas in plant cell morphogenesis. Classical cell wall models suggest that xyloglucan endo-transglycosylase activity is the primary catalyst (together with expansins) of controlled cell wall loosening through the transient cleavage and religation of xyloglucan-cellulose cross links. The genome of Arabidopsis (Arabidopsis thaliana) contains 33 phylogenetically diverse XYLOGLUCAN ENDO-TRANSGLYCOSYLASE/ HYDROLASE (XTH) gene products, two of which were predicted to be predominant xyloglucan endohydrolases due to clustering into group III-A. Enzyme kinetic analysis of recombinant AtXTH31 confirmed this prediction and indicated that this enzyme had similar catalytic properties to the nasturtium (Tropaeolum majus) xyloglucanase1 responsible for storage xyloglucan hydrolysis during germination. Global analysis of Genevestigator data indicated that AtXTH31 and the paralogous AtXTH32 were abundantly expressed in expanding tissues. Microscopy analysis, utilizing the resorufin b-glycoside of the xyloglucan oligosaccharide XXXG as an in situ probe, indicated significant xyloglucan endohydrolase activity in specific regions of both roots and hypocotyls, in good correlation with transcriptomic data. Moreover, this hydrolytic activity was essentially completely eliminated in AtXTH31/AtXTH32 double knockout lines. However, single and double knockout lines, as well as individual overexpressing lines, of AtXTH31 and AtXTH32 did not demonstrate significant growth or developmental phenotypes. These results suggest that although xyloglucan polysaccharide hydrolysis occurs in parallel with primary wall expansion, morphological effects are subtle or may be compensated by other mechanisms. We hypothesize that there is likely to be an interplay between these xyloglucan endohydrolases and recently discovered apoplastic exo-glycosidases in the hydrolytic modification of matrix xyloglucans.

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“…Henderson (7,8) contributed an approximate result, useful over a limited range of conditions for a single buffer mixture of a monoprotic acid and its conjugate base, but it is unfortunate that his name (and that of Hasselbalch, whose contribution is even more peripheral) is now replacing those of Guldberg and Waage. Regrettably, a recent paper in this Journal (9) perpetuates this misconception and the associated confusion.…”

Section: The Henderson-hasselbalch Equation: Its History and Limitationsmentioning

confidence: 99%