Lack of pH sensitivity

The most debated aspect of the snbject dnring the past half-century has been the initiation of oxidation. Initiation processes can be very varied and complex. They depend on both the polymer nature (PH) and the way that energy is brought to organic material (by temperature or radiation). Although the intermediate steps are not always totally known and understood (mainly because of the lack of sufficiently sensitive analytical methods to elucidate the corresponding structural changes), this problem simplifies considerably because all initiation processes lead finally to the formation of P and/or PO2 radicals. 

Several aspects affect the extent and character of taste and smell. People differ considerably in sensitivity and appreciation of smell and taste, and there is lack of a common language to describe smell and taste experiences. A hereditary or genetic factor may cause a variation between individual reactions, eg, phenylthiourea causes a bitter taste sensation which may not be perceptible to certain people whose general abiUty to distinguish other tastes is not noticeably impaired (17). The variation of pH in saUva, which acts as a buffer and the charge carrier for the depolarization of the taste cell, may influence the perception of acidity differently in people (15,18). Enzymes in saUva can cause rapid chemical changes in basic food ingredients, such as proteins and carbohydrates, with variable effects on the individual. 

Neurons are very sensitive to changes in the pH of the interstitial fluid surrounding them. Normally, the pH of arterial blood is 7.4. Under conditions of alkalosis, in which pH increases, the excitability of neurons also increases, rendering them more likely to generate action potentials. This inappropriate stimulation of the nervous system may lead to seizures, particularly in epileptics predisposed to them. Under conditions of acidosis, in which pH decreases, the excitability of neurons is depressed, rendering them less likely to generate action potentials. This lack of nervous system stimulation may lead to a comatose state. Severe diabetic acidosis or acidosis associated with end-stage renal failure will often lead to coma. 

Due to the rapidity of the spontaneous dismutation reactions, the steady-state concentrations of 02 achieved by chemical or by enzymatic reactions are usually quite low. The physical methods for detecting 02, although direct and unequivocal, are restricted to measurements of steady-state concentrations and are thus often found to lack of sensitivity. For distince, due to the reason mentioned above, when the EPR method was employed for studying the 02 production by xanthine oxidase, it was necessary to use a high concentration of the reactants and to work at elevated pH so... 

Use of the pH-sensitive membrane-impermeable flurophore pyranine based on the ratiometric method, which determines directly level of dissociation of pyranine from the ratio between the charged (nnprotonated) pyranine and total pyranine in the intraliposome aqneons phase Addition of impermeable DPX, which acts as a quencher to pyranine fluorescence, into the liposome external medium ensures lack of contribution of extraliposome medium pyranine fluorescence (18,22). This method is considered invasive as the pyranine has to be added in the hydration medium prior to liposome preparation and cannot be used for pH determination of intraliposome aqueous phase... 

Primary antibody diluted with inappropriate buffer. Use of PBS or TBS as an antibody diluent. Lack of stabilizing or carrier protein. Detergent in diluent. Check formula and compatibility of antibody diluent. A change of ion content and/or pH of the antibody diluent can cause a diminution in the sensitivity of the antibody. Addition of NaCI should be avoided. This problem is primarily seen with monoclonal antibodies. 57-60... 

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