PubMed · 23071
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G S Libinson. 1977. [Doxycycline. Its potentiometric titration].. https://pubmed.ncbi.nlm.nih.gov/23071/
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We describe an intermediate precision study on a capillary electrophoretic (CE) method for chlortetracycline. It is shown how in one setup the influence of the factors time, analyst, and equipment on the precision can be investigated. As different types of CE equipments were included, the transferability of the method could be examined. Both the qualitative and quantitative aspect of the method were investigated. It was shown that small adaptations in method conditions can have a large influence on the method transferability. Although the method could be transferred to different types of CE equipments, the precision of the method was found poor when the between-equipment variability was taken into account. Despite the use of an internal standard, the between injection variability was found rather high.
The interactions of calf thymus DNA with tetracycline (TC), 7-chlorotetracycline (CTC) and 6-dimethyl-7-chlorotetracycline (DMTC) were assessed employing spectrofluorometric and circular dichroism (CD) techniques. The Scatchard analysis revealed relatively lesser binding affinity of TC (Ka= 1.2 x 10(7) lmol(-1)) vis-a-vis CTC (Ka= 3.4 x 10(7) lmol(-1)) and DMTC (Ka= 3.0 x 10(7) lmol(-1)) with DNA. The data suggested both the intercalative and electrostatic nature of binding between the tetracyclines and DNA. The presence of Cu(II) augmented the interaction of tetracyclines with DNA, and resulted in red shift by 12 nm in CD spectra of tetracycline. The molar ellipticity (theta) also changed significantly for CTC and DMTC. The data unequivocally demonstrated the DNA binding potential of tetracyclines both in the presence and absence of Cu(II) ions in dark. The enhanced binding of tetracyclines in presence of Cu(II), ensuing conformational changes in DNA secondary structure to a varying extent, reflects differential reactivity of ligand chromophores.
On the base of element and metablism balancing, the mathematical model of the cultivation process with Streptomyces aureofaciens was developed, and the unknown parameters in the model were estimated with the method of nonlinear optimization. Firstly the energetic coefficient of CTC biosynthesis was gained, which was 1.8 - 2.8 mol-ATP x C-mol(-1). The macroscopic reaction rates were predicted in the process and compared with the experimental values. The results show that the model can preferably describe the relationships between several macroscopic reaction rates in the process and can supervise the optimization of CTC fermentation process theoretically.