ERIC BETZIG

Born 13 January 1960 Field of Work Applied Physics Institutes Howard Hughes Medical Institute and California Institute of Technology Thesis Near Field Scanning Optical Microscopy in 1988 Noble Prize Chemistry

Betzig worked at AT&T Bell Laboratories in the Semiconductor Physics Research Department. In 1996, Betzig left academics to become vice president of research and development at Ann Arbor Machine Company, then owned by his father. Here he developed Flexible Adaptive Servohydraulic Technology (FAST) but did not achieve commercial success.

Betzig then returned to the field of microscopy, developing photoactivated localization microscopy (PALM), and in 2006 he joined the Howard Hughes Medical Institute's Janelia Farm Research Campus as a group leader to work on developing super high-resolution fluorescence microscopy techniques.

Awards

Betzig was awarded the William L. McMillan Award in 1992 and the 1993 National Academy of Sciences Award for Initiatives in Research. In 2014, Betzig was awarded the noble peace prize in Chemistry.

Photo-activated localization microscopy (PALM or FPALM) and stochastic optical reconstruction microscopy (STORM) are widefield (as opposed to point scanning techniques such as laser scanning confocal microscopy) fluorescence microscopy imaging methods that allow obtaining images with a resolution beyond the diffraction limit. The methods were proposed in 2006 in the wake of a general emergence of optical super-resolution microscopy methods, and were featured as Methods of the Year for 2008 by the Nature Methods journal. The development of PALM as a targeted biophysical imaging method was largely prompted by the discovery of new species and the engineering of mutants of fluorescent proteins displaying a controllable photochromism, such as photo-activatable GFP. However, the concomitant development of STORM, sharing the same fundamental principle, originally made use of paired cyanine dyes. One molecule of the pair (called activator), when excited near its absorption maximum, serves to reactivate the other molecule (called reporter) to the fluorescent state.

A growing number of dyes are used for PALM, STORM and related techniques, both organic fluorophores and fluorescent proteins. Some are compatible with live cell imaging, others allow faster acquisition or denser labeling. The choice of a particular fluorophore ultimately depends on the application and on its underlying photophysical properties.

Both techniques have undergone significant technical developments,  in particular allowing multicolor imaging and the extension to three dimensions, with the best current axial resolution of 10 nm in the third dimension obtained using an interferometric approach with two opposing objectives collecting the fluorescence from the sample

Differences between PALM and STORM

PALM and STORM share a common fundamental principle, and numerous developments have tended to make the two techniques even more intertwined. Still, they differ in several technical details and a fundamental point. On the technical side, PALM is performed on a biological specimen using endogenously expressed fluorophores, in the form of genetic fusion constructs to a photoactivatable fluorescent protein. STORM instead uses immunolabeling of the sample with antibodies tagged with organic fluorophores. In both cases the fluorophores are driven by light between an active-ON and an inactive-OFF state. In PALM, however, photoactivation and photobleaching confine the life of the fluorophore to a limited interval of time, and a continuous emission of the fluorophore is desirable in between without any fluorescence intermittency. In STORM stochastic photoblinking of the organic fluorophores (typically brighter than fluorescent proteins) was originally exploited to separate neighboring dyes. In this respect, the more robust the blinking, the higher the probability of distinguishing two neighbouring fluorophores.


Posted by-
Supriya Joshi

Kinesiology >> Human Motion

Types of Motions

Classification based on path of motion

·  translatory motion (linear motion, translation)： a motion in which all parts of the moving body move toward the same direction

·  linear (or rectilinear) motion： a motion in which all parts of a moving body move in the same direction and the path follows a straight line
·  curvilinear motion： a motion in which the net motion of a moving body move toward the same direction although the path follows a curved line, e.g. the path of the center of mass of the body during level walking
		circular motion： a special form of curvilinear motion, which is the motion when a body moves along a circumference of a circle

·  rotary motion (angular motion, rotation)： a motion in which the object acts as a radius and all parts of the moving object rotate in the same angular direction and follow a circular path about a pivot point

·  angular motion： the rotary motion with one side of the moving object fixed, e.g. rotation of a limb

·  spin： the rotary motion with the axis of rotation around the center of mass

　

Classification based on repetition of motion

·  single motion： movement performed only once

·  repeated motion： same movement pattern that is done many times in a given time

·  reciprocal motion

·  oscillation： repeated motions in a small amplitude

·  pendulum motion： repeated motions like a pendulum

　

Classification based on degree of freedom

·  degree of freedom (DOF)： a minimum number of kinematic variables required to specified all positions and orientations of the segments in a body system i.e.

·  the number of planes in which the segments move

·  the number of the primary axes which the segments possess

·  Examples:

·  The joint that moves in one plane possesses one axis and has one degree of freedom

·  For the glenohumeral joint, there are three angular degrees of freedom and three linear degrees of freedom.

　

Classification based on relative segment kinematics

·  kinematic chain： a series of connected segment links

·  open kinematic chain motion： the joint motion with the distal segment moves free in space, e.g. raising lower leg or throwing a ball

·  closed kinematic chain motion： the joint motion with the distal segment is fixed, e.g. standing up or squatting down

·  In Neumann's book, "distal-on-proximal segment kinematics" and "proximal-on-distal segment kinematics" were used in stead of open and closed kinematic chain motion, respectively (Neumann 2002, p.7).

·  What kind of kinematic chain is performed as one-legged squatting?

　

Classification based on presence of muscle contraction

·  active motion： the motion that is caused by muscle contraction

·  passive motion： the motion that is created by sources other than muscle, such as from gravity

　

Classification based on joint kinematics

·  osteokinematic movement： movements between 2 bony segments

·  arhtrokinematic movement： movements between 2 articular surfaces