Absorbing biological molecules

MALDI is a method that allows for vaporization and ionization of non-volatile biological molecules from a solid-state or liquid phase directly into the gas phase. The presence of a solid or liquid matrix (around 1 part in 100-50,000), which strongly absorbs the laser radiation, spares the smdied species from degradation, by protecting them from the harsh effects of the laser. It results in the detection of intact molecules... 

Fluorescence has become one of the most powerful tools in the molecular life sciences . This is understandable because most biological molecules (particularly macromolecules) absorb light over the 200-800 nm spectral range. Many biomolecules are intensely fluorescent, and... 

Most conventional techniques for the determination of biological molecules or other species with similar properties use their ability to absorb ultraviolet or visible light, their fluorescence after excitation with light of the appropriate wavelength, or their electrochemical behaviour. It possible to enhance the detectability of some species by making them react with UV-visible absorbing or fluorescent compounds. Applied to complex matrices, these detection methods are at best only selective, because a wide variety of chromophores will give a response. 

After intramuscular injections of radiolabeled ceftiofur to cattle and swine, the compound was absorbed rapidly into the blood and eliminated mostly in urine (84). The tissue in which highest residue concentrations were observed at 12 h after the last dose was the kidney. Most of the radioactivity was found in the form of the microbiologically active primary metabolite, desfiiroylceftiofur, conjugated to macromolecules in plasma and tissues. Desfiiroylceftiofur cysteine was also found in tissues, plasma, and urine, whereas the desfiiroylceftiofur dimer was found in urine. It was suggested that since the binding of desfiiroylceftiofur to biological molecules is reversible, all of the ceftiofiir-related residues that contain the desfuroylceftiofur moiety have the potential to be microbiologically active. 

As pointed out above, the differential absorbance aA observed in VCD is very small, typically on the order of 5x10" to 5 x 10 5 of the infrared absorption A. In order to observe effects of this magnitude, sophisticated modulation techniques need to be employed, and instruments with very high light throughput and the most sensitive available detectors need to be constructed. This is particularly true for the study of biological molecules via VCD, since water is a necessary solvent for these studies, and the transmission of H,0 or DzO is low in the infrared spectral region. 

Although product analysis seems essential for the clarification of complex ET processes involving biological molecules, only few attempts have so far been made. Ohde et al. [15,35] conducted bulk electrolysis to determine spectrophotometrically some redox products of interfacial ET reactions. Recently, Sawada et al. [39] have developed a microflow coulometric cell with a hydrophobic membrane-stabilized O/W interface. This microflow cell can accomplish complete electrolysis, and thus determination of the number of electrons for complex ET reactions at O/W interfaces. Also, its use for an on-line spectrophotometric detection of electrolysis products was made [43]. Figure 8.5 shows the spectmm change of the electrolyzed solution for the ET between Fc in NB and Fe(CN)e in W. When relatively small potentials were applied to the microflow cell, Fc" could be detected in the electrolyzed solution. The characteristic absorbance peak at 620 nm showed an undoubted existence of Fc+ in the W phase as the electrolysis product. This result would also support the IT mechanism. In situ UV-visible spectroscopy [44 46] also deserves attention for its usefulness in product analysis and clarification of reaction mechanisms. 

Early attempts to functionalize biomaterial surfaces with biological molecules were focused on improving blood compatibility of cardiovascular devices, such as the artificial heart and synthetic blood vessels, by immobilizing heparin or albumin on polyurethane or Dacron . To enhance cell adhesion to biomaterial surfaces, entire extracellular matrix (ECM) proteins, such as fibronectin and laminin, have been used directly as coatings. However, because of the nonspecific manner of whole protein adsorption, most of the cell binding capability is often lost. Using a molecular templating technique, it may be possible to select which protein(s) to absorb on biomaterial surfaces. ... 

The free chlorine acts as a catalyst and a single chlorine atom may break down tens of thousands of ozone molecules before it returns to the troposphere. In the troposphere, chlorine reacts with hydrogen and forms hydrogen chloride that is rained out. Since ozone absorbs biologically-damaging UV radiation before it reaches the earth s surface, its depletion increases the risks associated with UV exposure. Ultraviolet radiation and over-exposure are linked with skin cancers, cataracts, and suppression of immune system response. In 1985, this problem started to attract everyone s attention by the dramatic announcement of the discovery of a hole in the ozone layer over... 

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