A, Ala, alanine

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Alanine
Valine
A, Ala, alanine
Phenylalanine
Proline
Methionine
Leucine
Isoleucine
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V, Val, valine
Valine has two methyl groups so it's somewhat
larger, rather more hydrophobic.
So here we have valine.
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F, Phe, phenylalanine
And we have phenylalanine.
This has this benzene ring, this unsubstituted
benzene ring, very hydrophobic
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P, Pro, proline
Here's proline. Proline is a little different
because it folds back onto the main chain of the
amino acid. So, strictly speaking, proline is an
imino acid instead of an amino acid but most
biochemists don't make that distinction.
So proline has all of these CH2's, so it's very
hydrophobic and it links back to the nitrogen of
the amino group of the amino acid.
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M, Met, methionine
methionine has a sulfur in here. It's one of two
amino acids with a sulfur, and again it's very
hydrophobic
Methionine,
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L, Leu, leucine
And then we have leucine and isoleucine.
Here's leucine, lot's of CH's, CH3's.
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I, Ile, isoleucine
Isoleucine is almost the same,
lots of CH2's and CH3's. So those are the
hydrophobic amino acids.
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Aspartic acid (aspartate)
Glutamic acid (glutamate)
Lysine
Arginine
Histidine
D, Asp, aspartate
it just has a CH2 and a carboxyl group, and so
that's an example of an acidic group.
Then we have the
charged amino acids
aspartate, glutamate, lysine, arginine,
histidine.
So aspartate is the simplest,
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E, Glu, glutamate
Glutamate has basically the same thing, but with
an extra CH2 in it.
See there are two CH2's and a carboxyl group
10
Chinese restaurant syndrome?????? ?????? ??????
MSG (monosodium glutamate) is abused as a flavor
enhancer in some restaurants, including some
Chinese restaurants. People who are sensitive to
MSG get a sensation like a clamp placed over
their head and tightened. Fortunately, the
sensation is temporary.
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K, Lys, lysine
this has a nitrogen forming
This is lysine the basic one,
this amino group at the end which is the basic
group and
this hydrocarbon chain
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R, Arg, arginine
Arginine has these three nitrogens and here we
can have a charge on this
Here's arginine.
guanidino group up here, so that's another basic
residue.
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H, His, histidine
And then we have histidine. Histidine is very
interesting because its pK is very close to the
pH in the body, and so the charge on
this nitrogen here can be positive or negative
depending on a variety of circumstances. And so
this is a residue you often find at active sites
of enzymes.
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Polar amino acids
Serine
Threonine
Tyrosine
Cysteine
Asparagine
Glutamine
Tryptophan
S, ser, serine
Polar means that they interact well with water,
so it's the opposite of hydrophobic. So these are
ones which have groups on them which will form
hydrogen bonds and interact well with water. So
this is the list
Serine has a hydroxyl group.
It's very simple just a methyleneand a hydroxyl
group
Let's move onto the polar amino acids.
serine, threonine, tyrosine, cysteine,
asparagine, glutamine, tryptophan.
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T, Thr, threonine
Then threonine has a
methyl group in addition.
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Y, Tyr, tyrosine
Tyrosine is a little more complex,
it has the benzene ring but it only has this
hydroxyl group out here making it polar.
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C, Cys, cysteine
Cysteine is the other amino acid with a sulfur in
it, and you can see it again is very simple with
that sulfur present.
And if we move onto cysteine.
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N, Asn, asparagine
this carbonyl and amine group here. This group
does not ionize, so it is not charged. It is not
acidic it's not basic. It doesn't ionize in the
body. It's polar because it interacts well with
water, but it's not ionized.
And then we have asparagine.
This again has a single CH2 group and now it has
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Q, Glu, glutamine
Same thing goes for glutamine.
Glutamine just has an additional CH2 group and
again it has
this polar group at the end.
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W, Trp, tryptophan
People usually put tryptophan in the group of
polar amino acids, but personally I don't really
agree with that.
It has this nitrogen here which can form hydrogen
bonds which gives it some polar character, but in
practice the non- polar nature of
these fused rings here actually is the dominant
feature. So although tryptophan is often put in
this group, it really has a mixture, as some of
the others do, of properties.
So finally, the last one on here is tryptophan.
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Glycine
G, Gly, glycine
is just a hydrogen atom. So this is basically
just a very quick run-through of the amino acids,
and as we talk about them more and see how
they're used, you'll get more familiar with them
and see how they work and see how their different
properties are important. Today what I really
wanted to get across was the nature of the forces
between amino acids and the properties of the
amino acids, which are important.
And then there's glycine,
the simplest one of all, which I kept until last,