Prof Sonia Antoranz Contera

Abstract:

The influence of the micropatterning of surfaces (in relation to their spreading and morphology) on the behavior of osteoblasts on different surfaces was investigated. Micropatterns were seen to be etched into silicon plates by photolithograhy and coated with a 250 nm tantalum layer. The samples were analyzed by Cryo-SEM (Scanning Electron Microscopy) (CamScan MaXim 2040). The elongation of cells was observed to be faster on deep line patterns than on shallow line patterns.

Abstract:

Trimeric Achromobacter cycloclastes Cu-containing nitrite reductase (CuNIR) proteins adsorbed on gold and graphite have been studied by ambient STM and in situ AFM. STM resolves them individually and in layers, distinguishing the sub-molecular individual units of the trimer. The Cu atoms are not visible to STM. STM shows that individual CuNIR denatures as it adsorbs on Au, although a deformed trimeric shape can be identified in some cases. CuNIR forms disordered layers on gold. On graphite, ordered self-assembled layers of CuNIR have been resolved by in situ AFM and ambient STM forming parallel rows whose separation distance corresponds to the size of one of the units of the trimer, 5nm. Ambient STM can achieve better resolution than in situ AFM in the images of the layers. We observe differences between domains showing the parallel row structure and unstructured parts of the CuNIR layer by in situ phase imaging AFM.

Abstract:

We have applied scanning tunnelling microscopy (STM) to the study of two proteins: pseudoazurin and apo-pseudoazurin. Both proteins adsorbed onto a Au (1 1 1) surface are visible to STM individually, forming into layers and multilayers, with currents from about 55 to 600 pA. The images reproduce well the expected dimensions laterally but not in the z direction. The apparent height of the proteins varies with the voltage polarity, being higher at negative sample voltages. The bias also affects their shape. Negative sample voltages of more than 1.5 V orient the proteins present on a gold terrace in parallel rows. The layer of water adsorbed on surfaces in ambient conditions can be related to our results to explain the reduced z dimensions, the asymmetry with the voltage polarity and the alignment of proteins at voltages more negative than -1.5 V.

Abstract:

Dimeric Arthrobacter globiformis amine oxidase in the holo and apo forms adsorbed onto a Au (111) surface have been observed by scanning tunnelling microscopy (STM) under ambient conditions. Individual protein molecules denature as they adsorb onto a bare Au surface, although they keep a dual appearance. Tapping atomic force microscopy images of individual proteins correspond well with the STM ones in the lateral direction. STM voltage affects the distance between the units of the denatured proteins: negative voltages separate them while positive ones get them together. Disordered as well as ordered layers of apo and holo proteins have been resolved by STM at molecular detail level. Individual proteins lying on the layers present a compact and a distinct dimeric shape, apo dimers looking bigger than holo dimers.