To ascertain interactions of urea with person nucleic acid functional groups by dissecting experimentally determined 23/ RT values for the interaction of urea with Na2NMPs, nucleosides, nucleobases and base analogs determined by VPO and distribution assays into additive contributions in the interaction of urea with each and every nucleic acid functional group, as well as with all the two Na+ ions for the 5′-NMPs:(3)where i represents the contribution to 23/RT in the interaction of urea using a unit surface region of surface type i. The term Na+Na+ represents the contribution of Na+ ions per formula unit (two for the 5′-NMP salts, 0 for nonelectrolytes), where Na+ is definitely the contribution from the interaction of urea with a Na+ ion to 23/RT, determined by evaluation of VPO information for the interaction of urea with Na carboxylates, amino acids and NaCl4. The assumption of additivity of contributions to 23 is supported by current studies of interactions of Hofmeister salts,five urea,four and glycine betaine6 with model compounds displaying the functional groups of proteins, at the same time as interactions of oligomers of ethylene glycol together with the surface exposed in melting nucleic acid oligomers.23 Deviations from additivity are of interest as examples of context-dependence arising from simultaneous interactions of a solute with two or additional functional groups around the model compound or biopolymer.Experimental Section5′-NMP Vapor Pressure Osmometry Particulars of sample preparation are described in supplemental. A Wescor Vapro 5520 vapor stress osmometer operating at ambient temperature was calibrated employing typical osmolality solutions from Wescor. All osmolalities have been corrected for discrepancies in between accepted literature values along with the Wescor typical solutions of sodium chloride.24 Triplicate osmolality measurements were produced on every sample and the standard errors determined as in Hong et al.24 Values of 23 for urea (component three)-Na2NMP (element 2) interaction at constant NaCl (element four) concentration had been obtained from osmolality data on four, 3 and two component options as follows:(four)(5)This generalization from the three element Osm equation to the predicament where a continual background of a fourth element (here NaCl) is present was previously utilized for DNA osmometry by Hong et al.25 Error propagation in 23,4Osm utilized eq three.DSPE-PEG-Maleimide 13 in Bevington and Robinson26 with regular errors and covariances of correlated parameters from several linear regression in the Osm(m2,m3,m4) and (Osm(m3,m4)) information (eqs 7.Ulipristal acetate 14.PMID:24202965 17, 7.19, 7.25 in Bevington and Robinson26 ). To check in the event the effect of urea on NaCl activity has a significantJ Am Chem Soc. Author manuscript; offered in PMC 2014 April 17.Guinn et al.Pageeffect, 34 was calculated as described in ref23 making use of urea-salt data from ref four and discovered to become negligibly smaller (4 of 23,4/RT).NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptNucleic Acid Base and Base Analog Distribution Assay Series of ten mL aqueous urea options with concentrations ranging from 0 molal were ready gravimetrically. The nucleobase or base analog was dissolved in hexanol, and 2 mL of this option had been added to each urea option. Samples were incubated inside a 25 shaking water bath for as much as 24 hours; precisely the same concentration ratio was observed in the event the samples have been study anywhere between 14 hours immediately after preparation. Absorbances of the water and hexanol phases were measured in a Cary 1 UV-visible spectrophotometer. From these data, we determin.
