The biochemistry of the steroids is of unique interest; no other group of relatively simple substances plays so versatile a role in biology. On the one hand are many highly potent steroids occurring in minute quantities e.g. sex hormones, corticosteroids, the vitamins D and the cardiac glycosides. In sharp contrast are certain sterols, exemplified in the animal kingdom by cholesterol - familiar, abundant, easily determined, yet singularly obscure in their physiological significance. In some restricted fields the functions of cholesterol are known. It is a precursor of the adrenocortical hormones (perhaps not an obligatory one ), and is probably important in the biosynthesis of sex hormones too. Present in the skin is 7-dehydrocholesterol, converted to vitamins D by ultraviolet light. Cholesteryl esters are found in large quantities, together with sphingomyelin, in the myelin sheaths of nerve fibres, where these lipids may have an insulating function necessary at least for saltatory conduction.

<p>Doktorska disertacija razmatra solubilizaciju holesterola pomoću okso derivata žučnih kiselina, upoređuje okso derivate žučnih&nbsp; kiselina&nbsp; sa hidroksi-derivatima istih u solubilizaciji holesterola i ispituje uticaj okso derivata na vijabilnost ćelijske membrane.&nbsp; Takođe, ispituje pKa vrednost različitih okso-derivata žučnih kiselina sa ciljem da se odredi kiselinska konstanta ovih slabih organskih kiselina. Cilj određivanja pKa vrednosti jeste determinacija rastvorljivosti žučnih kiselina. Kada se primenjuju oralno u raznim farmaceutsko-tehnolo&scaron;kim formulacijama, one se primenjuju u obliku soli, koje su rastvorne u vodi. Međutim, u kiseloj sredini želuca može doći do taloženja žučne kiseline i do daljeg sprečavanja delovanja soli žučne kiseline kao solubilizatora određenih farmacutski aktivnih supstanci. Doktorska disertacija ispituje i kritičnu micelarnu koncentraciju me&scaron;ovitih micela natrijumovih soli 3 žučne kiseline (holne, deoksiholne i 7-oksodeoksiholne kiseline) i natrijum-dodecil-sulfata u različitim molskim udelima na temperaturama od 0 do 50&deg;C pomoću spektrofluorifotometra pirenskom metodom.</p> / <p>The PhD thesis discusses solubilization of cholesterol by using oxo derivatives of bile acids and compares it&nbsp; with the hydroxy-derivatives of the same in the solubilization of cholesterol, and examines the impact of the oxo derivatives to the viability of the cell membrane. Also, the pKa value of different&nbsp; tested oxo-derivatives of&nbsp; bile acids is determined. The aim of determining the pKa values is to determine the solubility of bile acids. When administered orally in various pharmaceutical-technological formulations, they are applied in the form of salts, that are soluble in water. However, the acidic medium of the stomach may cause precipitation of a bile salt and further prevent the action of bile acid salts as a solubilizers of specific pharmaceutically active substances. The PhD&nbsp;&nbsp; thesis examined the the critical micelle concentration of the mixed micelles of sodium salt of 3 bile acid (cholic, deoxycholic, and 7-oksodeoksiholne acid) and sodium dodecyl sulphate at various temperatures, the mole fractions ranging from 0 to 50 &deg;C using the method of spectrofluoriphotometry by pirene as a probe molecule.</p>