Author/Authors :
Lam، نويسنده , , Karen P. and Hitchcock، نويسنده , , Adam P. and Obst، نويسنده , , Martin and Lawrence، نويسنده , , John R. and Swerhone، نويسنده , , George D.W. and Leppard، نويسنده , , Gary G. and Tyliszczak، نويسنده , , Tolek and Karunakaran، نويسنده , , Chithra and Wang، نويسنده , , Jian and Kaznatcheev، نويسنده , , Konstantin and Bazylinski، نويسنده , , Dennis A. and Lins، نويسنده , , Ulysse، نويسنده ,
Abstract :
Soft X-ray scanning transmission X-ray microscopy (STXM) was used to measure the Fe L2, 3 X-ray magnetic circular dichroism (XMCD) signal from individual, 30 nm diameter magnetosomes in a magnetotactic bacterium, specifically the marine vibrio strain MV-1. The Fe L2, 3 spectra recorded with circularly polarized X-rays from an elliptically polarizing undulator were very similar in shape and magnitude to those of fully saturated magnetite (Fe3O4). As previously determined by other techniques, our results show that the magnetic moments of individual magnetosomes arranged in linear chains in intact cells of strain MV-1 are all oriented in the same direction. The magnitude of the XMCD signal averaged over a chain of 9 magnetosomes in one cell is similar to that of single crystal magnetite. The spectral shape is slightly different, and indicates that magnetosomes have excess Fe(II), as noted in previous bulk studies of biogenic magnetite. To our knowledge, this is the first measurement of the XMCD of individual magnetosomes in magnetotactic bacteria.
Keywords :
Scanning transmission X-ray microscopy , xmcd , STXM , magnetotactic bacteria , magnetosomes , magnetite , Fe3O4 , Marine vibrio , Strain MV-1 , X-ray magnetic circular dichroism
