The quantitative contribution of several components to the BC of human semen has been investigated. The role of spermatozoa is negligible (less than 2%). Both the high-molecular components (proteins) and the HCO3-/CO2 system contribute about 25% to the BC. Therefore, about 50% of the BC of semen must be due to low molecular weight components other than HCO3-/CO2.
The influence of buffering substances and urea on the β-CD-mediated chiral separations of the dipeptides Ala–Phe and Ala–Tyr was studied in the pH range of 2.5–3.8. Only minor effects of the buffer substances on the chiral separation selectivity α were observed at a β-CD concentration of 15 mg/mL. In contrast, the selectivity improved at pH 2.5 but decreased at pH 3.8 upon the addition of 2 M urea. Complexation by β-CD resulted in a shift of the pKa values toward higher values which was more pronounced for the dd-enantiomers of both dipeptides than for the ll-enantiomers. Addition of urea further increased the pKa shift. The consequence of this pKa shift is an increase of the fraction of the protonated, positively charged form of the peptides which explained the improved chiral separation at pH 2.5 and the reduced selectivity at pH 3.8. A pKa shift by the addition of urea was also observed for N-tert-butyloxycarbonyl phenylalanine (BOC-Phe) as a model compound that is strongly complexed by β-CD.
And a new material for filling teeth that releases hydroxyl ions and a preventive gel with buffering substances can both effectively neutralize the acid produced in tooth plaque, even after being in the mouth for a long period. This has been shown by Anitha Persson at Umeå University in Sweden.
Caries, or tooth decay, both in connection with fillings in adult individuals and in the form of new cavities among the aging population of Sweden, is a growing problem. Preventing caries is one of the chief objectives of dental care today.
Anitha Persson has studied two ways of neutralizing the acid formed in tooth plaque following the ingestion of carbohydrates. This would prevent new caries attacks.
A new material for filling cavities proved to be capable of effectively neutralizing acid production in plaque, even after a long period in the patient’s mouth. Regular application of a fluoride gel containing buffering substances should be able to inhibit caries in elderly patient, unless they suffer from dryness of the mouth.
