Résumé
Objective: This study aimed to assess the destructive effects of citric acid, lactic acid and acetic acid produced from the fermentation of foods on primary teeth enamel
Methods: This in vitro, experimental study was conducted on 24 sound primary teeth. The teeth were polished with a fine abrasive paper under running water. Tooth pieces measuring 3×4×3mm were cut out of the teeth and stored in 100% humidity until the experiment. The specimens were divided into 3 groups [n=8] and immersed in acetic acid, citric acid and lactic acid, respectively. The enamel microhardness of specimens was measured by Vickers microhardness tester at baseline and 5 and 30min after immersion in the freshly prepared acid solutions
Results: Repeated measures ANOVA showed that the effect of immersion time on microhardness was significant [p<0.001]. Pairwise comparison among 0, 5 and 30 minutes time points using Bonferroni adjustment showed significant differences in microhardness at different time points [p<0.001]. Evaluation of the effect of type of acid on microhardness revealed that the microhardness was not significantly different in the three groups of acids [p=0.915]. Among the three understudy acids, only the reduction in microhardness from time 0 to 30 minutes was significantly different between lactic acid and acetic acid [p=0.042]
Conclusion: Citric acid, lactic acid and acetic acid were all capable of demineralization and reduction of enamel microhardness. A significant difference existed in the demineralization potential of acids [the highest for lactic acid]. However, this effect was more significant early after exposure
Résumé
The purification of biomolecules is a necessary step in many biochemical researches. In this regard, developments of convenient, specific and low cost methods of purification are of particular interest. Given the human hemoglobin [Hb] affinity toward some charged carbohydrates, interaction of this molecule with human chorionic gonadotropin [hCG] which is a glycoprotein hormone containing sialic acid, was examined. In the current study, we gathered evidence of free hCG and free Hb interaction using spectroscopic and radiometric techniques. Then, based on the affinity of hemoglobin [Hb] toward charged carbohydrates on human chorionic gonadotropin [hCG], a known sialic acid containing glycoprotein hormone, Hb-sepharose as well as native and denatured globin columns for isolation of the hormone were prepared. Sepharose-6B was activated by cyanogens bromide. Native Hb, normal globin and denatured globin were bound to cyanogen bromide-activated sepharose. Then, uptake of hCG by these gels were compared. Among the columns only native hemoglobin-sepharose column was able to catch a limited number of serum proteins such as hCG. Using the above column hCG hormone was purified with fold purification of 34 and efficiency of 80%. The chromatographic behavior of growth hormone [GH] and hCG in binding to the DEAE-Cellulose column were identical but GH showed no binding to Hb-sepharose column, indicating that the retention mechanism of hCG to Hb-sepharose column is not a simple ion exchange mode. Since globin had no property to attach to hCG but native Hbsepharose was able to catch hCG, the BPG cavity of Hb is suggested as the possible binding site for hCG to Hb