R-ATCHE-31

Proteins

Order is important (??)

No need to memorise, on the data sheet!

Conventionally written with the amine group to the left, and carboxylic acid to the right.

Secondary structure

Hydrogen bonds between peptide links (on backbone)

• This causes folding

"Backbone" refers to the repeating line of "C,C,N" that makes up the protein.

The C=O group of a "residue"(post amino acid) is slightly negatively charged, the N-H group of a reside is slightly positively charged. These two groups, but for different residues can form hydrogen bonds.

$\alpha$ helix - hydrogen bond between "every fourth residue".

When the molecule folds on itself, e.g.

Can form $\beta$-pleated sheets, where they bond between two sections of the overall polypeptide.

Tertiary

• Overall shape of protein
• Interaction of R groups (side groups)
• Non polar chains - dispersion (With other non-polar groups)
• $\delta- \implies \delta+$ Hydrogen bonding (not between the backbone, but sidechains)
• Ionic bonding ($COO^{-},NH_{3}^{+}$)
  • Dependant on pH (if not enough, just hydrogen bonding)
• Dipole-dipole
  • $S-H$($\delta+$) $\implies$$O=$($\delta-$)
• Di-sulfide bridge
  • $-SH$ + $HS-$
  • $-S-S-$ $(+2H^{+})$(this part is not needed)

Key words

• Fibrous vs globular
  • Used to describe the protein
  • Fibrous $\implies$ strandlike protein chains, quite "structural"
  • Globular $\implies$ globe like

Denaturing - Disrupting the shape, i.e. uncoiling

Usually, $H^{+}$ or $OH^{-}$ or heat, which can break pH dependant links.

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