Fig. 6. CD and intensity (I) of BMP receptors in A431 cells. A431 cells were cultured either in DMEM with 10% FBS or under serum starved conditions. Cells were grown in DMEM without FBS for 72 hours, then stimulated with BMP-2 or not stimulated. The cells were then fixed and the receptors labelled using polyclonal antisera against (A) BRIa and (B) BRII, and a secondary fluorescently labelled antibody. Cell membrane expression of receptors was visualised by confocal microscopy. Forty images were collected at the highest magnification. From these images the CD value of the receptors was calculated using ICS. The CD value of the background fluorescence caused by nonspecific labelling of the antibody was subtracted.