scholarly journals Topics in bound-state dynamical processes: semiclassical eigenvalues, reactive scattering kernels and gas-surface scattering models

1979 ◽  
Author(s):  
J.E. Adams
Keyword(s):  
Bound State ◽  
Surface Scattering ◽  
Reactive Scattering ◽  
Dynamical Processes

Surface Structure of A Liquid Perfluoropolyether Examined by Reactive Ion/Surface Scattering

1995 ◽  
Vol 380 ◽  
Author(s):  
T. Pradeep ◽  
S. A. Miller ◽  
H. W. Rohrs ◽  
B. Feng ◽  
R. G. Cooks
Keyword(s):  
Surface Structure ◽  
Metal Ion ◽  
Liquid Surface ◽  
Surface Scattering ◽  
Reactive Scattering ◽  
Self Assembled Monolayer ◽  
Molecular Systems ◽  
Surface Induced Dissociation ◽  
Chemical Sputtering ◽  
Surface Collision

ABSTRACTThis study shows that reactive ion/surface collisions can provide information on the surface structure of molecular systems. The microscopic structures of perfluorinated polyether (PFPE) liquid surfaces are characterized by ion/surface collision experiments in a mass spectrometer and the results are compared to those obtained with a fluorinated self-assembled monolayer (F-SAM) surface. Low energy (< 100 eV) beams of W+ and W(CO)6+ ions are used for surface-induced dissociation (SID) and ion/surface reactive scattering, while Xe+ and Kr+ beams are used for chemical sputtering experiments. Both the PFPE and F-SAM surfaces show similar SID fragments while reactions with W+ and W(CO)6+ lead to the scattered metal ion with multiple fluorine atoms attached. The main peaks in chemical sputtering spectra are similar for both surfaces as well. Both hydrogen probe beams and chemical sputtering confirm that the liquid PFPE surface is nearly free of impurities. Our results on both surfaces also suggest that the CF3 group of the monomer units is most likely projected outward from the bulk of the liquid surface.

CRYO-Electron Microscopy of the Acto-Myosin-ATP Complex

1990 ◽  
Vol 48 (1) ◽  
pp. 248-249
Author(s):  
John Trinickt ◽  
Howard White
Keyword(s):  
Electron Microscopy ◽  
Atp Hydrolysis ◽  
Myosin Head ◽  
Bound State ◽  
Cross Linking ◽  
Weakly Bound ◽  
Cryo Electron Microscopy ◽  
Myosin Subfragment 1 ◽  
Attached State ◽  
High Fraction

The primary force of muscle contraction is thought to involve a change in the myosin head whilst attached to actin, the energy coming from ATP hydrolysis. This change in attached state could either be a conformational change in the head or an alteration in the binding angle made with actin. A considerable amount is known about one bound state, the so-called strongly attached state, which occurs in the presence of ADP or in the absence of nucleotide. In this state, which probably corresponds to the last attached state of the force-producing cycle, the angle between the long axis myosin head and the actin filament is roughly 45°. Details of other attached states before and during power production have been difficult to obtain because, even at very high protein concentration, the complex is almost completely dissociated by ATP. Electron micrographs of the complex in the presence of ATP have therefore been obtained only after chemically cross-linking myosin subfragment-1 (S1) to actin filaments to prevent dissociation. But it is unclear then whether the variability in attachment angle observed is due merely to the cross-link acting as a hinge.We have recently found low ionic-strength conditions under which, without resorting to cross-linking, a high fraction of S1 is bound to actin during steady state ATP hydrolysis. The structure of this complex is being studied by cryo-electron microscopy of hydrated specimens. Most advantages of frozen specimens over ambient temperature methods such as negative staining have already been documented. These include improved preservation and fixation rates and the ability to observe protein directly rather than a surrounding stain envelope. In the present experiments, hydrated specimens have the additional benefit that it is feasible to use protein concentrations roughly two orders of magnitude higher than in conventional specimens, thereby reducing dissociation of weakly bound complexes.

Reactive scattering of crossed supersonic beams: Cl + CH2I2 → ICl + CH2I

1997 ◽  
Vol 92 (1) ◽  
pp. 71-75
Author(s):  
JIAN-XIN QI ◽  
GUANG-JUN WANG ◽  
KE-LI HAN ◽  
YONG-XIANG SHA ◽  
GUO-ZHONG HE ◽  
...  
Keyword(s):  
Reactive Scattering ◽  
Supersonic Beams
Sign in / Sign up

Export Citation Format

Share Document