Biological macromolecules, irradiation

With most solid polymers the G values for radical production, as determined by ESR, lie in the range 2 to 5. With biological macromolecules irradiated in the solid state comparable G values are obtained. 

Second, we tried the immobilization of DNA molecules as a potential target material for the immobilization of biological macromolecules. An aqueous solution of 1 mg/mL A.-DNA was spotted onto the surface of an azopolymer and covered with a cover glass, where the A.-DNA was stained with a fluorophore (YOYO-1 iodide, Molecular Probes Inc., Eugene, OR) in advance and the surface was then irradiated with the linearly shaped laser beam for 5 min, as shown in Fig. 3b. The surface was washed for 5 min in an aqueous solution and was then observed using... 

Following irradiation at low temperatures, the ESR spectrum of polymers shows changes in radical structure, ascribed to the movement of electrons and radicals to other and more stable sites. The behavior of many dried biological macromolecules is similar although a detailed interpretation may be more difficult. 

For a completely accurate crystal structure determination. X-ray scattering must be observed and recorded by reflection from the vast majority of hfcHattice planes associated with a given biological macromolecule crystal. That is to say that an accurate structural determination is only possible if the vast majority of reciprocal lattice points can be sampled. In order to achieve this, the classical approach has been to use a device like a four-circle diffractometer (Figure 6.15) in which biological macromolecule crystals are first mounted in a goniometer head located at the centre of the diffractometer and then irradiated with an intense beam of X-rays, after which X-ray reflections may be observed sequentially, one at a time, in... 

The repair of macromolecules and biological systems by electromagnetic irradiation. This process is wavelength dependent. An example is DNA repair by certain enzymes. 

The mechanisms of protection by these compounds have been evaluated for irradiated polymers. Many so-called protectors contain sulfhy-dryl groups and appear to operate by replacing or capturing the hydrogen atom lost by irradiating the macromolecule. It appears most reasonable to assume mat the same mechanism often occurs in biological systems. 

The question arises as to whether the irradiation introduced significant damage into the reacting macromolecules. The simplest procedure is to irradiate separately each reacting partner. Each can then be checked for effects on biological activity and for structural modifications. 

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