The conduction properties of alpha,omega-diaminoalkanes and hydrazine bridging gold electrodes are investigated using density functional theory in combination with Green's function techniques and group theory. We show that more than 99% of the current at low bias is carried by one channel of A' symmetry whose form is invariant to both the alkane chain length and realistic changes of the injection energy. The total conductance decreases exponentially with a decay constant of 0.73 angstrom(-1) with increasing chain length while the calculated gold- amine contact resistance is ca. 150 k Omega. (c) 2008 Elsevier B.V. All rights reserved.