Addition of sulphydryl groups to biliverdin

Summary Sulphydryl groups add to the central methine bridge of biliverdin in organic solvents as well as in aqueous solution (pH 7.4). The addition reaction is favoured by albumin but reversed in acid media.     

Action spectra for bilirubin photodisappearance

Summary The excitation wavelength dependence of bilirubin photodestruction, as measured by quantum yields, has been determined in benzene, chloroform-1% ethanol, chloroform-1% hexane, methanol-1% concentrated ammonia, pH 8.5 aqueous buffer and pH 7.4 aqueous buffer with added albumin. The results show that in the visible spectrum the 370–490 nm excitation wavelength region is very effective in the photodestruction, but excitation in the UV-region (<320 nm) is even more effective.The authors wish to thank the National Science Foundation (CHE 74-20877) and the National Institute of Child Health (HD 09026) for the generous support of this work.     

Characterization of the (Na+-K+)-ATPase from endometrial plasma membranes of immature mammals]

The (Na+-K+)-ATPase in plasma membrane from Mammiferous endometrium is characterized by the Mg/ATP ratio equal to one, and by a distinct affinity for Na+ (1.3 mM) and K+ (2 mM). The activity is maximum for pH 7.4-7.5 in presence of Mg++ 2mM and ATP 2 mM, Na+ 140 mM and K+ 10 mM.     

The Bohr effect and the red cell 2–3 DPG and Hb content in sherpas and europeans at low and at high altitude

Riassunto Europei e Sherpas hanno mostrato, dopo una permanenza di 3–4 giorni ad una altitudine di circa 5000 metri, normali P₅₀ (a pH 7.4 ed a pH 6.8) ed effetto Bohr (molto variabile negli Europei) ed elevato contenuto ematico di 2–3 DPG.     

Evidence for the existence of two carbonic anhydrase isozymes in rabbit ciliary body

Two carbonic anhydrase isozymes were found in the rabbit ciliary body. Their isoelectric points were determined to be pH 6.6 and pH 7.4, respectively. The total activity of the higher isoelectric point isozyme was higher than that of the lower isoelectric point isozyme.     

Evidence for the existence of two carbonic anhydrase isozymes in rabbit ciliary body

Summary Two carbonic anhydrase isozymes were found in the rabbit ciliary body. Their isoelectric points were determined to be pH 6.6 and pH 7.4, respectively. The total activity of the higher isoelectric point isozyme was higher than that of the lower isoelectric point isozyme.     

Zur Frage des pH-Optimums des Pepsins

Summary Natural and purified proteins were split by crystallized pepsin. The break down of substrates was followed by a turbidimetric method. pH optima were found from 1.5 to 3.8. Only unpurified egg albumin had two optima, crystallin had one in the acid range. Ovomucoid not being split by pepsin, the second peak at pH 3.79 is referred to conalbumin. While the disintegration of caseinogen becomes slow with decreasing acidity, this is not true for casein (paracasein) which is well split up to pH 3.28 (cows casein) or 3,73 (womens casein). Nevertheless, the optimum is in the range of 1.5–2.0, like most proteins. Above this limit, the following optima were found: fibrinogen 2.93, thrombin 2.78, edestin 3.08, crystallized hemoglobin 3.19, conalbumin 3.79.     

Regulatory properties of 14-day embryo and adult hen heart AMP-deaminase; the influence of pH on the enzyme activity

Summary The variation of kinetic parameters with pH for the reaction catalysed by the purified 14-day embryo and adult hen heart AMP-deaminase was shown to be similar but not identical. The pH-dependence of the half-saturation constant (K_0.5) is well pronounced, and the plot of pK_0.5 vs pH is manifested as a bell-shaped curve for both developmental forms of the enzyme. In contrast to that, the maximum velocity of the reaction (V_max) catalyzed by these enzymes does not change significantly in the range pH 5.6–7.4.Acknowledgments. The author wishes to thank Prof. M. Zydowo for interest in this work. This work was supported by a grant from the Ministry of Science, Higher Education and Technology within the project R.I.9, 01.06.     

The pH as controlling factor of shape and function of mitochondria

Riassunto È stato osservato che quando il pH intra-cellulare è più basso di quello plasmatico la forma dei mitocondri è prevalentemente a bastoncino, aumentando il pH (in condizioni sperimentali e patologiche) i mitocondri tendono a rigonfiare. Il fenomeno è anche dimostrabile spettrofotometricamente sui mitocondri isolati il cui rigonfiamento spontaneo regredisce abbassando il pH del mezzo. Il QO₂(N) e l'attività ATPasica aumentano a pH alcalini parallelamente al rigonfiamento mitocondriale. Il rapporto P/O si mantiene accoppiato fra pH compresi fra 6.6 e 7.4.È possibile che attraverso il pH si verifichi nella cellula un meccanismo di autoregolazione dell'attività funzionale dei mitocondri.     

Bestimmung der Eiweissbindung von Pharmaka in bikarbonatgepufferten Lösungen

Summary A gel filtration method is described for quantitative estimation of protein binding of drugs at 37 °C and pH 7.4 in solutions containing bicarbonate buffer.