Lecture 2

Lecture 2 - BCMB 3100 Lecture 2 Horton Chapter 2 Four types...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
BCMB 3100 – Lecture 2 Horton Chapter 2 • Four types of non-covalent interactions • Properties of the solvent of life: water • Review of acid-base concepts, pKa Noncovalent Interactions (reversible molecular interactions) • Charge-Charge (Electrostatic or ionic) • Hydrogen bonds • Van der Waals bonds • Hydrophobic interactions Noncovalent interactions are critically important to biology
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
+ H N R H H - R C O O H N R H H R C O O + - 0.28 nm ~ 40 to 200 kJ mol -1 Cl -1 Na +1 Formal Charges Non-Directional Charge is delocalized until salt bridge (or ion pair) is formed. Also called salt bridge or ion-pair interactions Charge-charge interactions Due to an asymmetric distribution of atoms with different electronegativities (H < C < N < O) . sp 3 Tetrahedron (slightly distorted) CH N C O H C H R + H 3 N R C O O - μ water = 1.8 Debye μ peptide = 3.5 Debye Molecular Diploes
Background image of page 2
δ + δ - Hydrogen Bond - a bond formed by sharing a hydrogen unequally between two dipoles. Donor - the atom with a higher affinity for, and is covalently attached to the hydrogen. Donor has a partial positive charge (dipole) . Acceptor - the atom that contributes a lone pair of electrons to the H- bond. Acceptor has a partial negative charge (dipole). Hydrogen Bonds "...the signifcance oF the hydrogen bond For physiology is greater than that oF any other single structural Feature.” - Linus Pauling Important H-bonds in Biology Hydrogen Bonds Found in Proteins Found in DNA
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
O H H Strong Weak O H H O H H 0.28 nm H-bond strength depends on: Distance D-H----A angle δ - δ - δ + O H H O H H O H H δ - δ + δ - δ - δ + δ + Hydrogen Bonds H N R R sp 2 N R H H N + R H H H sp 3 Acceptor Donor (Salt Bridge) Donor δ + sp 3 ~ 2 to 20 kJ mol -1 1. Identify the sp 3 (tetrahedral) and sp 2 (trigonal planar) atoms. 2. How many H-bonds can urea participate in? 3. Draw water molecules H-bonding to urea or the peptide. 4. Draw the approximate dipole (use the “cross-arrow”). N C N O H H H H N C N O H H H H ! + ! + ! - Urea CH N O CH H R + H 3 N R C O - Peptide Thought problem
Background image of page 4
Remember - Molecular dipoles are due to an asymmetric distribution of atoms with different electronegativities. (H < C < N < O) C H H H H Methane? van der Waals interactions As atoms approach each other they can induce weak dipoles called van der Waal’s induced dipoles as electrons move away from the approaching atom. C H H H H δ + δ - C H H H H δ + δ - C H H H H δ + δ - C H H H H δ + δ - ~0.36 to 0.44 nm E = ~0.4 to 4 kJ mol -1 van der Waals interactions
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
WATER • 60%-90% of most cells and tissues is water • Water is the solvent of life • it is ESSENTIAL to understand the
Background image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/07/2011 for the course BCMD 3100 taught by Professor Rose during the Spring '11 term at UGA.

Page1 / 20

Lecture 2 - BCMB 3100 Lecture 2 Horton Chapter 2 Four types...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online