Lecture 1 Biological Macromolecules.pdf

Biological  General Principles Physical biochemistry –physical properties of biological molecules includes proteins RNA and DNA(bioploymers) Various physical properties provide description of their structure from atomic level to multisubunit. Prop...

Biological  General Principles Physical biochemistry –physical properties of biological molecules includes proteins RNA and DNA(bioploymers) Various physical properties provide description of their structure from atomic level to multisubunit. Properties are studied through interaction and different kinds of radiation and their behavior in electromagnetic and centrifugal field. Quantitative aspect. Symmetry Mathematical ,diffraction method.  Configruration and Conformation Arrangement of atoms or groups of atoms in a molecule is described by the terms of configuration and conformation. Terms not identical. Configuration position of groups around one or more nonrotating bonds or around chiral centers, defined as atom having no plane or center of symmetry. Eg cis 1-2,dichlromethylene 2 chlorine atoms on same side of the nonrotating double bond.  configuration Require breaking double bond and then remake. Configuration imp biological molecules Stereochemistry of chiral molecules Sterioisomers -> identical in chemical composition ,are different in function  Conformational Analysis Conformations are different spatial arrangements of a molecule that are generated by rotation about single bonds.  Gauche/anti, eclipsed(staggered) on sides open chain single bond. (strain) Accurately described torsion angle θ about each freely rotating bond Torsion angle is the angle between two groups on either side of a freely rotating chemical bond. An important point: The terms anti and gauche apply only to bonds (or groups) on adjacent carbons, and only to staggered conformations.  Conformation Changing the conformation of a molecule does not make a new molecule but can change its properties The properly folded conformation of proteins referred to as native conformation ,functional form while unfolded or denatured conformation is nonfunctional –proteolysis of cell. Thus both are important for its shape and function but these represent distinct characteristics.  Helical symmetery Residues rotate and rise in a repeating manner along an axis Similar to screw symmetry Each residue is well defined point along the helix We can generate a helix by applying the rotational operator ^c and translational operator T of screw symmetry on a monomer unit. i having coordinates (x,y,z) ^c (x,y,z)+ T= (x,y,z) This form of screw symmetry is known as helical symetery Screw axis is helix axis E.g spiral staircase.