In nanotechnology, carbon nanotubes are evolving as 'hot spot' due to their applications as most sensitive biosensors. Thus, study of effect of biomolecular interaction is prerequisite for their electrical application in biosensors and bioelectronics. Here, we have explored this effect on electrical properties of carbon nanotubes with DNA as a model biomolecule. A stable conjugate of carbon nanotubes with DNA is formed via covalent methodology employing quantum dot as fluoropore and characterized with various spectroscopic, fluoroscopic and microscopic techniques. CNT-DNA adduct showed decreased transconductance (from 614.46 mu S to 1.34 mu S) and shift of threshold voltage (from -0.85 V to 2.5 V) due to change in Schottky barriers at metal nanotube contact. In addition, decrease in hole mobility (from 4.46 x 10(6) to 9.72 x 10(3) cm(2) v(-1) s(-1)) and increase in ON-linear resistance (from 74 k Omega to 0.44 M Omega) conclude large change in device parameters. On the one hand, this substantial change in device parameters after interfacing with biomolecules supports application of carbon nanotubes in the field of biosensors while on the other hand, the same can limit their use in future power electronic devices where stability in device parameters is essential. (C) 2012 Elsevier B.V. All rights reserved.