This is probably a bit of a naive question--but are there any complex synthetic molecules that are simultaneously Plastics AND Proteins?
It would seem a fascinating area of study, particularly if one was trying to find artificial muscles/skin/etc for prosthesis or Robots; that could run
on Glucose and heal itself to some degree...
Kind of a "Semi-Living" Substance...
.....RVM45
[Edited on 23-7-2009 by RVM45]greenimp - 23-7-2009 at 11:44
check out poly-gamma-glutamic acid. It gamma linked glutamic acid residues. Made from bacillus sp. Can be made into all kinds of interesting
things.
It is also can be made in anything from 30,000 MW to over 3,000,000 MW.
Xanthan gum, which is a sugar based polymer.
Also chiton, which is sugar based.
It really depends on what properties you want it to have. As far as "self healing" that is another story. Magpie - 23-7-2009 at 11:48
How about Nylon 66?UnintentionalChaos - 23-7-2009 at 16:36
Or the aramids for that matter. Any kind of nylon is a polypeptide as well.
As to the OP, proteins aren't alive. If you mean enzymes, no (they aren't alive either), but those are enormous in size and have to be precisely
folded, plus they degrade rapidly in many conditions and wouldn't be servicable as parts of any kind of plastic.chemoleo - 23-7-2009 at 17:57
Quote:
This is probably a bit of a naive question--but are there any complex synthetic molecules that are simultaneously Plastics AND Proteins?
Ever so slightly
Proteins ARE polymers, and some behave like plastics of sorts.
The definition of plastic is very broad, but usually it implies some very hydrophobic polymer (i.e. polystyrene, polycarbonate etc).
Proteins have hydrophobic groups, but their very backbone amides make it much less hydrophobic, and most (95%) proteins have many hydrophilic groups.
Hence 'plastic' properties of proteins are unlikely.
But biopolymers have been extensively studied, such as poly lactic acid, poly aspartate, cellulose, spider silk etc - and even these don't exactly
behave like what you probably understand of 'plastics'.
What IS done is to i.e. link natural protiens to polymers, such as polyethyleneglycol etc. But their use has been limited to research mostly.Ozone - 23-7-2009 at 18:27
A semantic dilemma:
The problem is that many "proteins" are crystalline, which is opposite of "plastic", or, amorphous. Rubbers and crosslinked polymers are neither (or,
rather, are both) and may exhibit viscoelasticity.
In other words, most homopolymerized amino acids yield regular, highly crystalline solids (read-non-flexible, brittle, etc.). Disrupting crystallinity
by making them highly irregular, e.g. random, in terms of amino acid repeat units, and, preferably, without hydrogen bonding side chains, might give a
"plastic-like" material.
Nylon(6,6) is a nice example in that it is a polyamide, but it is plastic because it does not engage in much interchain H-bonding (a behavior for
which most proteins are intrinsically designed).
See the proline-rich siderophoric foot protein (mfp) of the mussel (IIRC) Mytilus edulis, which is cool, and might be on the right track:
Self-healing behavior has been recently cited (I don't remember where I read it, check C&EN and Science for the last few months).
Cheers,
O3Reduce-Me - 25-2-2010 at 16:00
I know of something that might strike your fancy.
A person that collaborates with my lab is interested in such things (to a point)
He has the capacity to link proteins together through organic chemicals. An organic "wire" that has the capability of transferring electrons from one
protein to another (in vitro)
These reconstituted proteins that are connected to the molecular wire maintain catalytic activity outside of the cell.
Grimme, R. A., C. E. Lubner, D. A. Bryant, and J. H. Golbeck. Photosystem I/molecular wire/metal nanoparticle bioconjugates for the photocatalytic
production of H2. J. Am. Chem. Soc. 130:6308-6309.
He's had a lot more progess that has not been published yet.
If you don't have access to the paper then here is the abstract for the latest seminar he has given...
"This work describes the design, fabrication, characterization, and optimization of a biological/organic hybrid electrochemical half-cell that couples
Photosystem I, which efficiently captures and stores energy derived from sunlight, with a [FeFe]-H2ase enzyme, which can generate a high rate of H2
evolution with an input of reducing power. Using a method that does not depend on inefficient solution chemistry, the challenge is to deliver the
highly reducing electron from Photosystem I to the H2ase rapidly and efficiently in vitro. To this end, we have designed a covalently bonded molecular
wire that connects the active sites of the two enzymes. The key to connecting these two enzymes is the presence of a surface-located cysteine residue
that can be changed through genetic engineering to a glyine residue, and the use of a molecular wire terminated in sulfhydryl groups to connect the
two modules. The sulfhydryl group at the end the molecular wire serves to chemically rescue one of the iron atoms of a [4Fe-4S] cluster, thereby
generating a strong coordination bond. The molecular wire connects the FB iron-sulfur cluster of Photosystem I and the distal iron-sulfur cluster of a
Fe-Fe/Fe-Ni hydrogenase enzyme. The result is that the low-potential electron can be transferred without loss and at high rates directly from PS I to
the H2ase enzyme. The PS I-molecular wire-H2ase complex will be tethered to a gold electrode through a baseplate of cytochrome c6, which will
additionally serve as a conduit of electrons from the gold to Photosystem I. Cytochrome c6 and the other proteins will be covalently bonded to the
electrode through a self-assembling monolayer of functionalized alkanethiols The device should be capable of transferring electrons efficiently from
PS I to the H2ase to carry out the reaction: 2H+ + 2e- + 2hv --> H2. Our results to date are as follows. Photosystem I, which was rebuilt using the
C13G/C33S variant of PsaC, was connected to the C98G HydA variant of the [Fe-Fe]-H2ase from Clostridium acetobutylicum using a 1,6-hexanedithiol
molecular wire. Cytochrome c6 and ascorbate were added to the solution to function as soluble electron donors to PS I. Upon illumination of the
construct in a sealed N2-purged vial for 8 to 15 hours, H2 was produced at rates ranging from 0.3 to 2.1 µmol H2 mg Chl-1 h-1, depending on the
sample. After a rough optimization of solution conditions, the rate increased approximately two-fold to 31 µmol H2 mg Chl-1 h-1. Control experiments
were performed to verify light-induced H2 production. The controls included the absence of the following substrates: light, rebuilt PS I with variant
PsaC, variant [FeFe]-H2ase, and 1,6-hexane dithiol; as well as the substitution of wild-type PS I and wild-type [FeFe]-H2ase. All of the controls
failed to generate H2. We are in the process of optimizing conditions to maximize the rate. Funded by the US DOE (ER46222). "
