Biological systems human digestive

Another wide application of mass spectrometry is the detection and characterization of post-translational modifications such as myristoylation, phosphorylation, disulfide bridging, etc. The detection and localization of post-transla-tional modifications has been a rapidly developing area of mass spectrometry due to the functional importance of these modifications in biological systems. An example of this was recently shown for the case of the human rhinovirus HRV14 [10]. Electron density maps from crystallography data indicated a myristoylation of VP4. Mass analysis of VP4 also indicated a mass difference of 212 Da (consistent with myristoylation of VP4). Additional experiments with proteolytic digestion and tandem mass spectrometry were able to localize the modification to the N-terminus of VP4. 

A series of our studies has shown that the pungent principle of radish, i.e MTBI, can be labile and reactive in food systems and in the human digestive tract to form various sulfur-containing compounds. We subsequently describe below some of the biological activities of the reaction products and their action mechanisms. 

Dental enamel is a unique biological system that provides a hard surface for the teeth, and enables them to reduce food to particles sufficiently small for effective attack by the digestive enzymes. Provided that it remains free from disease, human enamel can withstand a lifetime of crushing work without becoming fractured or completely worn away. Enamel is capable of performing this function only because of its most abundant constituent, hydroxyapatite, which gives it a hardness intermediate between that of iron and carbon steel. 

Lester et al. [24] have described a robotic system for the analysis of arsenic and selenium in human urine samples which demonstrates how robotics has been used to integrate sample preparations and instrument analysis of a biological matrix for trace elements. The robot is used to control the ashing, digestion, sample injection and operation of a hydride system and atomic absorption instrument, including the instrument calibration. The system, which routinely analyses both As and Se at ppb levels, is estimated to require only... 

Enzymatic. Biological procedures for cholesterol removal make use of microorganisms that produce enzymes to convert cholesterol into innocuous compounds. Several enzymatic systems are being investigated in different cormtries of the world. Most systems use a cholesterol reductase that converts the cholesterol into coprostanol and coprosterol (52, 57). These converted compounds are very poorly absorbed by the digestive system and pass through intact. Several investigators have isolated and characterized Eubacteria able to convert cholesterol into coprostanol from rat, baboon, and human feces. Leaves of cucumber, soybeans, corn, and beans are known to contain similar enzymes (45, 57, 58). Lactobacillus acidophilus has also been reported to metabolize cholesterol (51). 

The correlation between chemistry and biology is so large that at present we came across such subjects a "biochemistry". There are many a topics in biology which are quite dependent on knowledge of chemistry, e.g. biomolecules, working of various human systems such as blood circulation, digestive system etc. 

Methane is formed in biological processes that occur in low-oxygen environments. Anaerobic bacteria, which flourish in swamps and landfills, near the roots of rice plants, and in the digestive systems of cows and other ruminant animals, produce methane FIQURE 18.14). It also leaks into the atmosphere during natural-gas extraction and transport. It is estimated that about two-thirds of present-day methane emissions, which are increasing by about 1% per year, are related to human activities. 

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