Peptide bond
A peptide bond is a chemical bond formed between two molecules when the carboxy group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O). This is a dehydration synthesis reaction, and usually occurs between amino acids.The resulting C-N bond is called a peptide bond, and the resulting molecule is called an amide. Polypeptides and proteins are chains of amino acids held together by peptide bonds. The backbone of PNA is also held together by peptide bonds.
The C-N bond has a partial double bond character (with the Nitrogen atom attaining a partial positive charge and the oxygen atom a partial negative charge) and the molecule can normally not rotate around this bond. The whole arrangement of the four C,O,N,H atoms as well as the two attached carbons in a peptide bond is planar.
A peptide bond can be broken by amide hydrolysis (the adding of water). The peptide bonds in proteins are metastable, meaning that in the presence of water they will break spontaneously, releasing about 10 kJ/mol of free energy, but this process is extremely slow. In living organisms, the process is facilitated by enzymes. Living organisms also employ enzymes to form peptide bonds; this process requires free energy.
He has had to neglect his own farm since
trouble. Now this is too much. He is dead tired of it all, and so am
last night. We have been thinking of getting away from it all when
by the arm. Do you, too, agree to his giving away the hay.html">hay.html">hay.html">hay.html">hay.html">hay you need
yourselves? Do you, too, want to go/go.html">go to America, away from your
originally mine. If our flocks die, there will be no alternative;
not be worth living.html">living because of the poverty and want round about us.
out.
On hearing this, Brandur's mood softened somewhat. I expected to be
cannot go on living in this fashion any longer.
Pass your last days with us! exclaimed Gudrun. Have you, then,
You've never said a word of this to me.
I have no intention of leaving Holl. That I have never meant to do.
move over here and live with me. I could then let you have what
hay in the old stack.html">stack? Everything depends on that.
The hay! The hay! the old man.html">man said. Still harping on the hay--the
It's sheer nonsense to think that the hay in that stack is enough to
it I will not throw that tiny mouthful to all the four winds. It
to me alone. No, I will not part with it as long as there is a spark
Looking at him, Gudrun knew from experience that he was not to be
sky over the wilderness streaked with threatening storm clouds.
Gudrun gave up. The tears.html">tears rushed to her eyes, as she twined her arms
have angered you. I shall not come here again.
The old man felt the teardrops on his face, the heavy woman's tears,
the darkness at mid-day. Yet in his mind's eye he could see.
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