Synthesis of cholesterol-polyamine carbamates: pKa studies and condensation of calf thymus DNA

Abstract

Novel cholesterol-polyamine carbamates have been prepared and their pK a s determined potentiometrically for conjugates substituted with up to five amino functional groups and the binding affinity for calf thymus DNA has also been determined; these polyamine carbamates are models for lipoplex formation with respect to gene delivery (lipofection), a key first step in gene therapy.

Non-Viral Gene Delivery Systems Based on Cholesterol Cationic Lipids: Structure-Activity Relationships

“…Although the exact mechanism by which polycationic lipids mediate transfection requires more detailed investigation evidence in literature points towards the notion that the success of these reagents arises from a couple of factors: the abnormally low pKa's (pKa <7) of the polyamines, a direct result of the number of amino groups present and the methylene spacings between them (Stewart et al, 2001;Keller et al, 2003;Geall et al, 1999;. The effects of the regiochemical distribution of positive charges along the polyamine moiety in DNA condensing agents were studied (Geall et al, 2000). DNA condensation is dependent upon the number of positive charges, the regiochemical distribution of charges of polyamines (determined by the pKa of each amino group), and the local salt concentration.…”

“…Polyamines were successfully used as a component of polycationic lipids (Geall et al, 2000;Blagbrough et al, 2003;Oliver et al, 2004). Polyamines are a class of naturally occurring compounds that display excellent nucleic acid binding and condensing properties.…”

“…The significant transfection activity attained was attributed to an improved cell binding and uptake of the lipoplexes promoted by the presence of cholesterol (Crook et al, 1998) and/or better stability of the lipoplex in serum (Simberg et al, 2003). In 1991, Gao et al reported the synthesis and application of the cholesterol-based cationic lipid 3-β-[N-(N′,N′-dimethylaminoethyl)carbamoyl]-cholesterol (DC-Chol, 1a), which was combined with DOPE to transfect mammalian cells (Gao & Huang, 1991 (Zhdanov et al, 1998;Gao & Hui, 2001;Geall et al, 2000;Percot et al, 2004;Ding et al, 2008;Medvedeva et al, 2009;Maslov et al, 2010). The cationic amphiphiles containing cholesterol as a hydrophobic residue possess a high transfection activity and a low toxicity, finding use in the studies of both the structure-activity relationships and membrane fusion mechanisms Kearns et al, 2008).…”

Modulation of Neuronal Voltage-Activated Calcium and Sodium Channels by Polyamines and pH

“…[24][25][26] As the IC 50 of polyamine inhibition of mixed neuronal VACC currents has been reported as high 15 we explored the actions of polyamines under a range of conditions likely to alter the positively charged polyamines and potentially increase binding affinity. 27 This involved using physiological Ca 2+ and Mg 2+ concentrations 28,29 (1.1 mM) to minimize confounding competition between polyamines and the ions permeating the VACC. The inhibitory actions of spermine, spermidine and putrescine were compared and described with models…”

Synthesis of 2,2'-Bis(3,6,9-triazanonyl)-4,4'-bithiazole and Related Compounds as New DNA Cleavage Agents

“…However, it was comparatively difficult to protonate the two central nitrogen atoms in both side chains of 3a (which have diethylenetriamine moieties) presumably due to electronic repulsion between positive charges on nitrogen atoms separated by an ethylene group. 19,20) In contrast, 4b possesses amido nitrogen atoms at 6-position in both side chains, so remaining four amino groups were expected to be protonated; however, only one amino group in each side chain of 4a was protonated because 4a possesses ethylenediamine moieties in both side chains. Since 3a and 4b were expected to have a total of four positively-charged nitrogen atoms in the neutral condition, the affinity of 3a for DNA would be almost the same as that of 4b.…”