Whats the difference with the same products with different peptide sequence

[little billy]

Can someone explain what the N-Terminus and C-terimus all about.

What I understand is that the N-Terminus have classification ie.
Amine (I know this one as NH2 and is orgainic compound)
Acetyl
Biotin
Flourescein
Can someone explain these?
Is PEG an Amine then?

What I understand is that the C-Terminus has also classification ie
Amide
or Free Acids
This is where I get a bit confussed as i notice some peptides have a amine for the C-terminus as well. Does that make an amine the same as a Amide if its on the C-terminus. I dont understand. Is it an amine or an amide or both. I have no idea. Can someone explain it.

Because ive seen same products with the different sequence Im hoping if I can find answers to my questions of why that is. Because if there is a difference I want to buy the right peptide. Maybe thats why some people reckon its a waste of money and other say it works. I just want to no what im buying.
THANKS

 

[gridlock]

as far as i know the c-terminus is related to carboxyilic(or might be just carboxyil)???? groups of peptides while the n terminus relates to amines (amines have got a basic nitrogen atom at the heart of them so hence the "N")

an amide is a compound that has both carbon and nitrogen linked as its functional group.

every amino acid has got an carboxyl and amine group but they arent necessarily linked as a functional group like in an amide if that makes sense.

i think peg has spacers with carboxy (-COOH) and amino (-NH2) termini. so that wouldnt make it an amine as an amine is a basic nitrogen atom with a lone pair. the nitrogen is the only functional atom in this.

reading back that kind of confuses even me but it makes basic sense until you get one of the cleverer guys on here to chime in

in fact dont quote me on any of that stuff above i'm tired enough as it is