{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

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

Info iconThis preview shows pages 1–6. 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 Document Right 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 significance 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 Document Right Arrow Icon
O H H Strong Weak O H H O H H Weak 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 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.
Background image of page 5

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

View Full Document Right Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}