26 Important Concepts 26 important Concepts 1.Polypoptidos- amide linked poly- 6 ly Pure made 26 Important Concepts 26 Important Concepts Hem Protein ical polymers of phosphate 11.DNA Synthesis-asc s used to ooo.AU.C.G aReoha29ndn8spmepn8spaeproteciggr8ps. C.G Its in ar ry b. 1212 26 Important Concepts 1. Polypeptides – amide linked poly-amino acids • Most natural polypeptides are made from only 19 different L-amino acids and glycine. • All amino acids have three- and one-letter abbreviations corresponding to their common names. 2. Amphoteric – amino acids can be both protonated and deprotonated. 3. Enantiomerically Pure Amino Acids – made using fractional crystallization of diasteromeric derivatives or by enantioselective reactions starting with appropriate achiral precursors. 26 Important Concepts 4. Polypeptide Structure – varied: linear, cyclic, disulfide bridged, pleated sheet, α helical or superhelical, or disordered. • Structure depends upon size, composition, hydrogen bonding, electrostatic forces and London forces. 5. Separation – depends mainly upon size- or charge￾based ability to bind to solid supports. 6. Sequencing – combines selective chain cleavage and amino acid analysis of the shorter polypeptide fragments. 7. Synthesis – utilizes end-protected amino acids that are coupled by dicyclohexylcarbodiimide. After selective deprotection, the chain can be further extended. The use of solid supports (Merrifield synthesis) allows automation. 26 Important Concepts 8. Heme Proteins – the oxygen binding proteins hemoglobin and myoglobin contain a heme, enveloped by the polypeptide chain. Oxygen is reversibly bound to an iron (II) atom at the center of the heme. 9. Nucleic Acids – biological polymers of phosphate￾linked, base-bearing sugars. • RNA – phosphate, ribose, A, U, C, G • DNA – phosphate, deoxyribose, A, T, C, G Hydrogen bonding between A-T and C-G results in an antiparallel dimeric double helix containing complementary base sequences. During DNA and RNA synthesis this helix unwinds and functions as a template. Groups of three bases called codons specify each amino acid in the corresponding protein. 26 Important Concepts 10. DNA Sequencing – uses restriction enzymes, radioactive labeling and specific chemical cleavage reactions. The resulting smaller fragments are analyzed by electrophoresis. 11. DNA Synthesis – a silica support is used to build up the growing oligonucleotide with the help of base, alcohol, and phosphite-phosphate protecting groups. 12. PCR – the polymerase chain reaction makes multiple copies of DNA