[mimi999]

Ok so I am really stuck and just hope someone will explain to me in simple english the following

The reaction between penicillin and an –NH2 group on the protein chain of the enzyme that catalyses the production of the new cell wall during bacterial replication is well established and is described. However, this cannot be the complete story, as the side chain (R) was found to be necessary for activity against bacteria. It therefore seems likely that the R group must bind in some way to the enzyme to hold the penicillin molecule in the correct place.
State and explain the type of intermolecular attraction that you would expect the R group of penicillin G to form with the side chain of a leucine residue in a protein chain. Why would this attraction be more likely to form to a leucine residue rather than a serine residue?

I would be so so happy if someone explains it I have re -read my book and still have no answer and need one asap
kind regards
ps. doing chemistry as part of my course however not that good at it but its part of my biology course

[mimi999]

anybody?

[Dan]

What is the R group of Penicillin G?

[mimi999]

it does not state what is the R group however in the book there were an example and for the Penicillin G was  bezene ring connected to CH3 if that helps?

[kriggy]

Thats it.
what is the difference between the two mentioned amino acids?

[discodermolide]

it does not state what is the R group however in the book there were an example and for the Penicillin G was  bezene ring connected to CH3 if that helps?

There are lots of penicillins. The "older ones were all designated by "penicillin G, F and so on. This depended upon the group in the side chain of the β-lactam ring. So to answer Dan's question; penicillin G tells you the structure! Now I'm not sure how this arose, it may have originated from the mould that made it. But I'll find out.
 

[Babcock_Hall]

It is a forum rule that you try to provide an answer before we can help.  I'll try to point you in the right direction.  Can you list out the common intermolecular forces?  Which of these can or cannot be experienced by the side chain of leucine?

[mimi999]

ok bare with me I shall have more complete explanation by tomorrow as reading again , I have read again looked again would that be because of polarity  to do with it polar  and non polar in terms of the difference? so one is polar and one isnt ? just not sure about London forces ,hydrogen bond ? But hopefully I read again and will have my answer tomorrow , I actually do want to understand chemistry as well as possible as it really puts me in a panic state 

[mimi999]

so here is my answer
 alkyl groups are non polar .  Serine  is polar . Leucine will interact  via London forces with penicillin am i on the right direction  ?

[Babcock_Hall]

Yes, but I think your answer could be much more specific and discuss the intermolecular forces involved.  When I assess the polarity of a side-chain, I ask myself certain questions:  Does it have a charge, is it a H-bond donor, is it a H-bond acceptor, are there bonds with a dipole moment, is there a large portion of the chain which is purely hydrocarbon.  These questions are related to the well-known intermolecular forces, such as ion-dipole attraction, hydrophobic force, etc.  My preference is to assess the polarity of a molecule or group as a kind of summing up of all of the individual contributions.