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2-Nitrobenzyl derivatives have been used for several years as photolabile protecting groups in synthetic organic chemistry. Recently, P3-1-(2-nitro phenylethyladenosine 5'-triphosphate "caged ATP" was synthesized and its photolysis was shown to generate ATP in situ. This and related reactions have great potential for structural and kinetic studies of both intact and soluble biological systems and it is thus important to define the kinetic characteristics of the photolytic reaction. Caged ATP (2.5 mM) was photolyzed at 347 nm by a single 30-nsec pulse from a frequency-doubled ruby laser of 25 mJ energy to generate 500 microM ATP. The kinetics of the overall reaction were determined by monitoring the kinetics of ATP-induced dissociation of actomyosin, a reaction of known kinetic characteristics. Release of 500 microM ATP was found to be controlled by a process having a rate constant of 2.2 X 10(9) [H+] sec-1 at 22 degrees C at pH 5.8-9.5, which corresponds to 220 sec-1 at pH 7. This process is believed to be the breakdown of an aci-nitro compound, which was identified on the basis of its spectral properties and the photochromicity of related 2-nitrobenzyl compounds.

A scattered-light method using depolarized incident light is used for nondestructive measurement of 3-D stress distribution. In this method, scattered light on the plane of the incident light sheet in the interior of photoelastic model is observed from the direction perpendicular to the plane. By optical slicing of the model with such a light sheet the stress distribution can be determined in each slice. Experiments for the case of a frozen stress sphere model under diametral compression are made to show the usefulness of the proposed method.

Three-dimensional stress distribution in a model of the human ankle joint under static loading has been measured nondestructively in real time by using the scattered-light polarizer photoelastic method with depolarized incident light. The maximum shear stress distribution in the interior of the model is obtained by optical slicing with the incident light sheets. The stress pattern in the interior of the model can be examined visually as contour lines of the maximum shear stress distribution as well as in 2-D plane-light photoelasticity.

Tissue distribution of radioactive carbon from [U-14C]glucose in the mouse in vivo was studied by whole-body autoradiography. The mice were frozen with Dry-Ice-acetone at 0.5, 1, 5 and 30 min, 1 and 24 hr and 1 and 3 weeks after intraperitoneal injection of [U-14C]glucose. Whole-sagittal sections of the frozen mouse, obtained by using a microtome in a cryostat, were dried in a cryostat and autoradiographed. The resulting dry autoradiographs are called untreated autoradiographs in the present work. The sections were then fixed in cold 6% (w/v) HClO4, dried at room temperature and again autoradiographed. Autoradiographs that have undergone this process are referred to as treated autoradiographs. In both untreated and treated autoradiographs, within 1 min following injection of the labeled glucose, the abdominal cavity had the highest autoradiographic density. At 1 hr, density became highest in Harder's, sublingual and duodenal glands, large intestinal mucosa and tongue, and after 3 weeks, no autoradiographic denisty was present.

The isopachics of a birefringent object were obtained as a moiré pattern, see Kihara et al., Appl. Opt.15, 3025 ( 1976). This paper describes experiments that separate the isopachics of a birefringent object by using the immersion method real-time polarization holography. The sign of the isopachics is accurately determined in real time by inserting a wave front retarder in the optical path of the illuminating beam and observing the shift of the fringe pattern.