The focus of this research is to determine the strength of non-covalent interactions between oligonucleotides and b-cyclodextrins using electrospray ionization mass spectrometry (ESI-MS). The cyclodextrin-oligonucleotide complexes have been used to improve cellular uptake of antisense nucleotides in gene therapies. The advantage of ESI-MS in the examination of these interactions over other analytical techniques relies on the soft ionization of the inclusion complex and the ability to quantitatively determine the strength of host-guest interactions from changes in peak area due to host-guest complexation. Quantitative determination of the strength of binding (K_b) between individual nucleotides and b-cyclodextrin in the inclusion complex will be calculated from changes in peak areas of interest from mass spectra. All samples will undergo a cation exchange procedure using an ammonium hydroxide/deionized water solution. Concentrations of complexed and uncomplexed ligands determined from peak area will be used to calculate the strength of the binding constant (Kb) between oligonucleotides of selected composition and b-cyclodextrins. Mass spectra will be acquired in triplicate a on a Varian 1200L Quadrupole MS/MS in the negative ion mode. Peaks that suggest a 1:1 complex between the b-cyclodextrins and the individual nucleotides have been found. Rate constants should be able to be determined from the fraction saturation of b-cyclodextrins on the oligonucleotide based upon the m/z ratio of the peak area of interest. The binding constant of the multiple equilibria between the cyclodextrins and the oligonucleotide, including cooperativity, should be able to be calculated from sum of the molecular weight of the bound cyclodextrins and the oligonucleotide, based upon simple assumptions. The results acquired from ESI-MS were also compared against traditional spectrophotometric methods. Ratios of antisense oligonucleotides and b-cyclodextrins will be optimized for maximum peak area. Changes in the strength of binding between nucleotides/oligonucleotides and modified b-cyclodextrins will be examined.