Colorimetric assay of HIV-1 Tat protein and peptide

Colorimetric analysis has been used to determine the biomolecules interaction in a solution with that can be indicated from color changes that can be observed either by spectrophotometer or naked eyes. Gold nanoparticles (GNP) which originally exist as pink color solution will aggregate and turn to purple color when mixed with salt solution. It was used as the basic solution and it mixed with aptamer probe and when NaCl salt solution was added to the mixture, the color changes was observed from pink to purple in the presence of HIV-1 Tat protein target. GNP are capable of adsorbing small oligonucleotides due to their propensity for electrostatic attractions, hydrophobic absorption, and covalent binding. In this experiment, GNP adsorbed the aptamer probe covering its surface preventing salt solution from interacting with GNP. Colorimetric detection is use to prove the interaction that happened in the mixing solution of aptamer and protein by observing the color changes with the presence of target and measuring the absorbance of wavelength of the solution. The wavelength shift has been observed due to changes in color. The value of wavelength for GNP observed was 522nm and shifted in wavelength can be observed in the presence of tat protein at 531.83nm while for tat peptide at 529.84nm.