Anslyn pp. 753 – 806


p. 755 — Interesting how differently medicine characterizes value distributions.  Consider one distribution of polymer weights given here — 10, 10, 10, 10, 10, 15,000, 16,000, 17,000, 18,000, 19,000, 20,000.  Medicine is interested in 15,000 which one might call the median weight.  Translate this into cancer survival, with a more reasonable distribution of numbers say 3, 10, 12, 13, 13, 14, 16, 20, 25, 36, 60.  The median suvival in months is what medicine (and patients) want to know.   The outliers of 3, 60 screw up the average, but roughly half of patients will live less than 14 months and half live more — with one or two lucky ones living 3 or more years.  Patients also want to know about the longest survivors, because it might be them.  Patients with amyotrophic lateral sclerosis (ALS, Lou Gehrig’s disease) are always told about Stephen Hawking, who has lived nearly 5 decades rather than 5 years with the disorder. 

p. 756 — I suppose there wasn’t time or space to chemically describe just what a leucine zipper actually is, but it’s a beautiful thing, and the hydrocarbon side chain of leucine (CH2-CH- (CH3)2) is the tooth of the zipper.  For a picture see http://upload.wikimedia.org/wikipedia/commons/thumb/e/e8/Leucine_zipper.png/220px-Leucine_zipper.png.    Leucine zippers are common in proteins binding DNA, and zips them together allowing combinatorial binding of adjacent DNA sequences.  

p. 757 — Poor explanation of gel permeation chromatography (GPC).  Polymers of a size fitting into the pore size of the column spend more time in the column and are eluted last.  Not explained is how larger polymers get through the column at all.  They get through because the column is packed with beads with pores of a certain size.  Polymers not entering the pores of the beads, flow around (italics) the beads and are eluted faster.  

p. 763 –>  The stuff on dendrimers is interesting, particularly the two ways of making them and the interior holes they contain.  People are trying to find uses for them in drug delivery, particularly against cancer. You can link multiple copies of a drug to the outside of a dendrimer if the periphery is of the correct chemistry (this is polyvalency, a term from immunology).  This is important particularly for work involving the immune system as all antibodies are polyvalent. 

p. 775 — Nice to see how derivatives of buckyballs are made.  I wouldn’t have thought that Diels Alder would work with C60, as it seems so complete.  The disparity in lengths between the 6 – 6 bonds (at 1.38 Angstroms nearly the classic 1.34 of ethylene and still close to that of benzene at 1.40) and 6 – 5 bonds (1.45 — nearly the classic 1.54 for an sp3 – sp3 carbon carbon bond).  Do the ring currents on one side of the buckyball cancel those on the other.  

p. 776 — (n/2 – 10) should be (n/2) – 10

p. 778 — Any idea why SH is attraced to gold (as opposed to OH, NH, CH, PH, SiH)?  Clearly true as in OH (CH2)n SH, only the SH bonds to gold. 

p. 778 – 779 — An opportunity was missed to show how putting a small hole in the class slide allows you to form a lipid bilayer (exactly two lipid layers thick), and use it to study permeability, ion transfer, etc. etc. 

p. 792 — Why not just give the O-H bond strength (119 kiloCalories/mole) instead of saying that it’s very strong? 

p. 796 — What is methyaluminoxane ?

p. 799 — Group transfer polymerization is truly beautiful chemistry.   How did Webster ever find it?

The big enchilada chapter is coming up, and is the reason I’ve read the book sequentially so far.  Hopefully I’ll understand sophisticated molecular orbital theory \ along with molecular dynamics, and most importantly,  the limitations of both after I’ve read it.  I’ve never trusted molecular dynamics simulations of proteins, membranes, ion channels  etc. etc., not because I think their wrong, but because of the possibility of tweaking parameters to get what you want.   Hopefully the next chapter will give me the chops to read books on computational organic chemistry, articles on protein folding.  A big order but A&D have been great so far.

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