Influence of systematic error on the shape of the Scatchard plot of tRNAPhe binding to eukaryotic ribosomes

Scatchard plots of tRNAPhe binding to poly(U)-programmed human 80 S ribosomes can be curved, either concave upwards or concave downwards, depending on the experimental conditions. The influence of a systematic error on the shape of the Scatchard plots has been analysed in a model experiment where the binding proceeds at two independent sites. The Scatchard plot for this binding model has a concave-upwards shape. When the concentration of the ribosomes is kept constant, a small systematic error in tRNA concentration changes this Scatchard plot markedly to a concave-downwards plot as though a co-operative interaction occurred. In contrast, when the tRNA concentration exceeds the ribosomal concentration and their concentration ratio is constant, the Scatchard plot is stable with respect to the systematic error. We suggest the latter type of experiment to be more appropriate. The results also imply a non-co-operative interaction of tRNAPhe with the 80 S ribosome.

The laser magnetic resonance spectrum of the ν1 band of the CCN radical in its state

Vibration–rotation transitions in the ν1, band of the CCN free radical in the [Formula: see text] state have been observed by CO laser magnetic resonance (LMR) spectroscopy. The observations have been combined with existing diode laser data to determine the parameters of an N2 effective Hamiltonian modified to include the Renner–Teller effect in the [Formula: see text] state explicitly. The LMR observations are well modelled by estimated Zeeman parameters that take into account non-adiabatic vibronic interactions. The analysis suggests a small systematic error in the diode laser measurements and leads to a revision of the band origin, ν1, to 1923.252 92 (42) cm−1.