Guys my first year chem teacher said, and I quote almost verbatim:

>>8590255
bumperino for interestino

>>8590255
It's been years since my chem studies but I started thinking what interactions the side chain could have with water: it cannot be protonated, deprotonated and it cannot form hydrogen bonds. Therefore, it must be hydrophobic.

>>8590273
What about this?
"The side chain contains an amide group, constituting a carbonyl (CO) and amine portion (NH 2 ). This amide group can hydrogen bond
via two lone pairs on the carbonyl oxygen, and one on the amine nitrogen, as well as two hydrogen atoms on the amine section.", and "Indeed, studies have suggested
that the stability of collapsed, globular polyQ chains results from an extensive hydrogen-bonding network between glutamine molecules, where glutamine−glutamine hydrogen bond interactions outweigh interactions with the surrounding solvent environment."
http://pubs.acs.org/doi/abs/10.1021/jp307442f

>>8590273
The H bound to the N can actually make hydrogen bonds with a O, and so can the lone pair of the N with a hydrogen.
Furthermore, for a site to be totally hydrophobic, you'll have to consider WdW polar/polar interactions

>>8590286
>>8590301
Of course, yes, the lone pairs on the oxygen and the hydrogen on the nitrogen can form hydrogen bonds. However, if the lone pair on N is delocalized I suppose it can't form H-bonds?

>>8590332
The lone pair won't but the H will, as their binding pair will be even more localised on the N. plus, once again, you'll have t consider polarity

File: aastructures.jpg (188KB, 680x901px) Image search: [Google]

188KB, 680x901px

>>8590255
Well every resource i could find marks it as polar, also your reasoning sounds on point. Are you sure she meant glutamine?

>>8590400
Yeah, I even checked with the notes of other people.
To give it a bit more context, she was talking about lactate dehydrogenase and how said gln residue is present to give specificity to the methyl portion of pyruvate. A quick search in literature gives nothing about this. I hope it's just a case of her talking out of her depth.

>>8590488
Maybe try asking around, either her or someone else with similiar credentials.

>>8590400
>she
when did OP say it was a she teacher?

>>8590255
Resonance reduces the polarity by distributing the charge of the lone pair across a higher number of atoms. What puzzles me is how C2 can contribute to resonance since it's sp3. I'm going to assume that the glutamine residue in a LDH enzyme has been structurally modified to allow resonance between the N and the carboxyl group.

>>8590255
I mean, it depends on how you classify polar.

The amide is polarized, yes, because of resonance and will have a significant dipole. Compared to alanine, it's highly polar. That said, it doesn't bear a charge (like lysine or asparagine at physiological pH), so compared to those residues it's not very polar. In the context of proteins, it is more likely to be hydrophobic because it's probably more stabilized by nonpolar residues than it is by the aqueous environment.

>>8590255
I don't think she's right. The resonance structure of the terminal amine indeed lowers the polarity but it still shows a significant dipole. Also try to draw the resonance structure and you will end up with an OH-group that also can form H-bonds. This only means that the H-bond is propably less strong due to two possible resonance structures. But now related to the context of LDH. Probably only the disattraction of the gln and the methyl residue of pyruvate is not very high and it just fits neat into the active site. Pyruvate is a very polar molecule and it would not make much sense for the enzyme to introduce a very apolar group to "stabilize" the interaction with such a small methyl group.
>>8590560
The amine on C2 does not delocalize. Otherwise people would be wasting their time getting enantiomerically pure glutamine because it could racemize.