Direct observation of global protein motion in hemoglobin and myoglobin on picosecond time scales

Science ◽  
1991 ◽  
Vol 251 (4997) ◽  
pp. 1051-1054 ◽  
Author(s):  
L Genberg ◽  
L Richard ◽  
G McLendon ◽  
R. Miller
Keyword(s):  
Time Scales ◽  
Direct Observation ◽  
Protein Motion

Direct Observation of Protein Motion during the Photochemical Reaction Cycle of Bacteriorhodopsin

Langmuir ◽  
2007 ◽  
Vol 23 (13) ◽  
pp. 7225-7228 ◽  
Author(s):  
Zoltán Bálint ◽  
Gergely A. Végh ◽  
Anca Popescu ◽  
Mihai Dima ◽  
Constanta Ganea ◽  
...  
Keyword(s):  
Direct Observation ◽  
Photochemical Reaction ◽  
Protein Motion ◽  
Reaction Cycle

scholarly journals Reactions of DOPA (3,4-dihydroxyphenylalanine) decarboxylase with DOPA

1979 ◽  
Vol 183 (2) ◽  
pp. 361-368 ◽  
Author(s):  
A Minelli ◽  
A T Charteris ◽  
C B Voltattorni ◽  
R A John
Keyword(s):  
Steady State ◽  
Time Scales ◽  
Direct Observation ◽  
Equilibrium Constants ◽  
Active Part ◽  
Stopped Flow ◽  
Step Rate ◽  
Multiple Reactions ◽  
Absorbing Material ◽  
Different Time Scales

The study of DOPA (3,4-dihydroxyphenylalanine) decarboxylase by steady-state methods is difficult because multiple reactions occur. The reaction with DOPA was studied at enzyme concentrations between 20 and 50 micrometer by direct observation of the bound coenzyme by using stopped-flow and conventional spectrophotometry. Four processes were observed on different time scales and three of these were attributed to stages in the decarboxylation. The fourth was attributed to an accompanying transamination that renders the enzyme inactive. It was clear that much, if not all, of the 330 nm-absorbing coenzyme present in the free enzyme plays an active part in the decarboxylation, since it is converted into 420 nm-absorbing material in the first observable step. An intermediate absorbing maximally at 390 nm is formed in a slower step. Rate and equilibrium constants have been determined and the ratio of decarboxylation to transamination was estimated to be 1200:1.

scholarly journals Allostery through Protein Motion at Different Length and Time Scales

2016 ◽  
Vol 110 (3) ◽  
pp. 221a
Author(s):  
Colin A. Smith ◽  
Adam Mazur ◽  
David Ban ◽  
Stefan Becker ◽  
Christian Griesinger ◽  
...  
Keyword(s):  
Time Scales ◽  
Protein Motion

Direct Observation of Heat Exchanger Deposits by Cross Sectioning

1967 ◽  
Vol 25 ◽  
pp. 364-365
Author(s):  
R. W. Anderson ◽  
D. L. Senecal
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Heat Exchanger ◽  
Direct Observation ◽  
Cross Sections ◽  
Preparation Method ◽  
Specimen Preparation ◽  
Flowing Water ◽  
Transmission Electron ◽  
Deposit Layer

A problem was presented to observe the packing densities of deposits of sub-micron corrosion product particles. The deposits were 5-100 mils thick and had formed on the inside surfaces of 3/8 inch diameter Zircaloy-2 heat exchanger tubes. The particles were iron oxides deposited from flowing water and consequently were only weakly bonded. Particular care was required during handling to preserve the original formations of the deposits. The specimen preparation method described below allowed direct observation of cross sections of the deposit layers by transmission electron microscopy.The specimens were short sections of the tubes (about 3 inches long) that were carefully cut from the systems. The insides of the tube sections were first coated with a thin layer of a fluid epoxy resin by dipping. This coating served to impregnate the deposit layer as well as to protect the layer if subsequent handling were required.

Application of a Simple Cold Stub to the Direct Observation of Frozen Hydrated Sand

1973 ◽  
Vol 31 ◽  
pp. 212-213
Author(s):  
John M. Wehrung ◽  
Richard J. Harniman
Keyword(s):  
United States ◽  
Surface Water ◽  
Direct Observation ◽  
Controlled Study ◽  
Clay Particles ◽  
Organic Debris ◽  
Rock Formations ◽  
Water Tables ◽  
Permeable Rock ◽  
Natural Means

Water tables in aquifer regions of the southwest United States are dropping off at a rate which is greater than can be replaced by natural means. It is estimated that by 1985 wells will run dry in this region unless adequate artificial recharging can be accomplished. Recharging with surface water is limited by the plugging of permeable rock formations underground by clay particles and organic debris.A controlled study was initiated in which sand grains were used as the rock formation and water with known clay concentrations as the recharge media. The plugging mechanism was investigated by direct observation in the SEM of frozen hydrated sand samples from selected depths.

Direct Observation of the Diffusionless β → β + ω Transformation in Titanium Alloys

1971 ◽  
Vol 29 ◽  
pp. 122-123
Author(s):  
N. E. Paton ◽  
D. de Fontaine ◽  
J. C. Williams
Keyword(s):  
Electron Microscope ◽  
Titanium Alloys ◽  
Direct Observation ◽  
Dark Field ◽  
X Ray Diffraction ◽  
Resistivity Measurements ◽  
Selected Area Electron Diffraction ◽  
Ti Alloys ◽  
Thin Foils ◽  
Field Device

The electron microscope has been used to study the diffusionless β → β + ω transformation occurring in certain titanium alloys at low temperatures. Evidence for such a transformation was obtained by Cometto et al by means of x-ray diffraction and resistivity measurements on a Ti-Nb alloy. The present work shows that this type of transformation can occur in several Ti alloys of suitable composition, and some of the details of the transformation are elucidated by means of direct observation in the electron microscope.Thin foils were examined in a Philips EM-300 electron microscope equipped with a uniaxial tilt, liquid nitrogen cooled, cold stage and a high resolution dark field device. Selected area electron diffraction was used to identify the phases present and the ω-phase was imaged in dark field by using a (101)ω reflection. Alloys were water quenched from 950°C, thinned, and mounted between copper grids to minimize temperature gradients in the foil.

A New 1000kv Electron Microscope

1969 ◽  
Vol 27 ◽  
pp. 100-101
Author(s):  
J.L. Williams ◽  
K. Heathcote ◽  
E.J. Greer
Keyword(s):  
Electron Microscope ◽  
Direct Observation ◽  
High Voltage ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Specimen Thickness ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
Dynamic Experiments ◽  
Conventional Instrument

High Voltage Electron Microscope already offers exciting experimental possibilities to Biologists and Materials Scientists because the increased specimen thickness allows direct observation of three dimensional structure and dynamic experiments on effectively bulk specimens. This microscope is designed to give maximum accessibility and space in the specimen region for the special stages which are required. At the same time it provides an ease of operation similar to a conventional instrument.

LVSEM: Past Present and Future

1990 ◽  
Vol 48 (1) ◽  
pp. 364-365
Author(s):  
James B. Pawley
Keyword(s):  
Field Emission ◽  
Line Width ◽  
Time Scales ◽  
Silicon Oxide ◽  
Beam Current ◽  
High Brightness ◽  
High Beam ◽  
Fixed Charges ◽  
Beam Voltage ◽  
Deposited Metal

Past: In 1960 Thornley published the first description of SEM studies carried out at low beam voltage (LVSEM, 1-5 kV). The aim was to reduce charging on insulators but increased contrast and difficulties with low beam current and frozen biological specimens were also noted. These disadvantages prevented widespread use of LVSEM except by a few enthusiasts such as Boyde. An exception was its use in connection with studies in which biological specimens were dissected in the SEM as this process destroyed the conducting films and produced charging unless LVSEM was used.In the 1980’s field emission (FE) SEM’s came into more common use. The high brightness and smaller energy spread characteristic of the FE-SEM’s greatly reduced the practical resolution penalty associated with LVSEM and the number of investigators taking advantage of the technique rapidly expanded; led by those studying semiconductors. In semiconductor research, the SEM is used to measure the line-width of the deposited metal conductors and of the features of the photo-resist used to form them. In addition, the SEM is used to measure the surface potentials of operating circuits with sub-micrometer resolution and on pico-second time scales. Because high beam voltages destroy semiconductors by injecting fixed charges into silicon oxide insulators, these studies must be performed using LVSEM where the beam does not penetrate so far.

Direct Observation of Monolayer Zones in Al-wt 4% Cu

1990 ◽  
Vol 48 (1) ◽  
pp. 14-15
Author(s):  
B. Jouffrey ◽  
D. Dorignac ◽  
A. Bourret
Keyword(s):  
Solid Solution ◽  
Synchrotron Radiation ◽  
Direct Observation ◽  
Supersaturated Solid Solution ◽  
Original Model ◽  
X Ray ◽  
Image Position

Since the early works on GP zones and the model independently proposed by Preston and Guinier on the first steps of precipitation in supersaturated solid solution of aluminium containing a few percent of copper, many works have been performed to understand the structure of different stages in the sequence of precipitation.The scheme which is generally admitted can be drawn from a work by Phillips.In their original model Guinier and Preston analysed a GP zone as composed of a single (100) copperrich plane surrounded by aluminum atomic planes with a slightly shorter distance from the original plane than in the solid solution.From X-ray measurements it has also been shown that GP1 zones were not only copper monolayer zones. They could be up to a few atomic planes thick. Different models were proposed by Guinier, Gerold, Toman. Using synchrotron radiation, proposals have been recently made.

Clinical Update: Functional Capacity Evaluations and Disability

1998 ◽  
Vol 3 (2) ◽  
pp. 4-5
Author(s):  
Glenn Pransky
Keyword(s):  
Direct Observation ◽  
Functional Capacity ◽  
Work Capacity ◽  
Functional Capacity Evaluation ◽  
Whole Body ◽  
Validity Of Results ◽  
Job Tasks ◽  
Capacity Evaluation ◽  
Physical Abilities ◽  
The Relationship

Abstract According to the AMA Guides to the Evaluation of Permanent Impairment, a functional capacity evaluation (FCE) measures an individual's physical abilities via a set of activities in a structured setting and provides objective data about the relationship between an impairment and maximal ability to perform work activities. A key distinction between FCEs and self-reported activities of daily living is that the former involve direct observation by professional evaluators. Numerous devices can quantify the physical function of a specific part of the musculoskeletal system but do not address the performance of whole body tasks in the workplace, and these devices have not been shown to predict accurately the ability to perform all but the simplest job tasks. Information about reliability has been proposed as a way to identify magnification and malingering, but variability due to pain and poor comprehension of instructions may cause variations in assessments. Structured work capacity evaluations involve a set of activities but likely underestimate the individual's ability to do jobs that involve complex or varying activities. Job simulations involve direct observation of an individual performing actual job tasks, require a skilled and experienced evaluator, and raise questions about expense, time, objectivity and validity of results, and interpretation of results in terms of the ability to perform specific jobs. To understand the barriers to return to work, examiners must supplement FCEs with information regarding workplace environment, accommodations, and demotivators.

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