G, where r = phenyl ethyl group is the most powerful

Antibiotics: Antibiotics are specific chemical substances derived from

or produced by living organisms that are able to suppress >> << life processes of other organisms. First

antibiotics have been isolated from microorganisms, but some of them being received from

higher plants and animals. Over 3000 antibiotics were found

but only a few dozen are used in medicine. Antibiotics

most widely prescribed class of drugs includes 12% >> << prescriptions in the United States. Penicillins first antibiotic discovered natural products with

form Penicillium. In 1928, Sir Alexander Fleming, professor of bacteriology

St. Mary's Hospital in London, was

cultivation of Staphylococcus aureus. He said braking band

where mold spores from growing. He named the mold Penicillium

hihit. It was found that secretion was effective form >> << to gram-positive bacteria. Penicillins and cephalosporins are called beta-lactam antibiotics

and is characterized by three main structural requirements >> <<: fused beta-lactam structure (shown in blue and red >> << ring-free carboxylic acid group (shown in red

bottom right), and one or more substituted amino acid side chains (see

in black). lactam structure can be viewed as a covalent link >> << , pieces of two amino acids - cysteine ​​(blue) and valine

(red), penicillin-G, where R = phenyl ethyl group is the most powerful

all derivatives of penicillin She has several shortcomings and. <<. >> is valid only for gram-positive bacteria. This can be broken

stomach acid and stomach badly and irregularly

absorbed into the bloodstream. In addition, many diseases

producing staphylococci are capable of producing an enzyme capable inactivate

penicillin-G. various semisynthetic derivatives were made

which overcome these disadvantages. powerful electron-attracting groups attached to the amino acid side chain

like in phenethicillin prevent attacks acid. bulky group attached to the amino acid side chain provides steric interference

which interfers with the enzyme equipment

to disable pencillins is methicillin. See.

Table 2 for structures. Finally, if the polar character increases, as in ampicillin or carbenicillin << >> is a big activiity of strattera gram-negative bacteria. << >>