What is poly-hydroxybutanoate and what do you use it for?

Question

What is the chemical reaction and conditions used to make this type of polymer? Is this a common polymer? .. **confusedd**

Answer 1

Polyhydroxybutanoate is a biopolymer, and that is a polymer produced by a living plant, animal fungus, bacterium, or other biological entity. It's used in the transmembrane transport of Ca2+ ions across vesicle bilayers. It is presently being used in research on the premise that if biopolymers, rather than the petrochemical industry, could be used as the feed stock for the making of plastics, then--unlike fossil fuels--this would be a renewable resource.
For example, the first commercially produced plastic made from cellulose (a polymer) was cellulose acetate or celluloid

Name of the enzyme or organism used to synthesise the above biopolymer is called: Alcaligenes eutrophus

Answer 2

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Answer 3

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Answer 4

1

Answer 5

It is a sythetic biopolymer that is being used in the research of transporting drugs across cellular membranes.

http://www.actabp.pl/pdf/1_2000/79-85.pdf

Answer 6

Hope the following websites help

Answer 7

depolymerase
poly[(R)-3-hydroxybutanoate]n + H2O = poly[(R)-3-hydroxybutanoate]n-x + poly[(R)-3-hydroxybutanoate]x; x = 1-5

Answer 8

are you sure that is the correct spelling...?

try going to: ChemFinder.com

Answer 9

huh?

Answer 10

Biomimetic polyesters and their role in ion transport across
cell membranes
Zbigniew Jedliñski, Piotr Kurcok, Gra¿yna Adamus and Maria Juzwa
Centre of Polymer Chemistry, Polish Academy of Sciences, 41-800 Zabrze, Poland
Received: 25 October, 1999
Key words: biomimetic poly-(R)-3-hydroxybutanoate, supramolecular alkali metal catalysts, ion transport
through phospholipid bilayer membranes
Syntheses of biomimetic low-molecular weight poly-(R)-3-hydroxybutanoate mediated
by three types of supramolecular catalysts are presented. The utility of these synthetic
polyesters for preparation of artificial channels in phospholipid bilayers capable
of sodium and calcium ion transport across cell membranes, is discussed. Further
studies on possible applications of these bio-polymers for manufacturing drugs of prolonged
activity are under way.
Two types of natural aliphatic polyesters
having the structure of poly-(R)-3-hydroxybutanoate
(PHB) are present in living systems:
High-molecular-weight polymers (Mw up to
hundred thousands) produced in prokaryotic
cells as microbial storage material
Low-molecular-weight polymers (20/120
mers) present in prokaryotic and eukaryotic
cells, forming complexes with poly-Ca-phosphate
as building blocks of channels in cell
membranes, responsible for ion transport
across a membrane. The low-molecularweight
polyesters are present also in human
blood plasma [1].
The presence of low-molecular-weight PHB
polymers in living cells and their obvious importance
in life processes have attracted at-
Vol. 47 No. 1/2000
79–85
QUARTERLY

Presented at the 7th International Symposium on Molecular Aspects of Chemotherapy, September
8–11, 1999, Gdañsk, Poland.

Financial support from the State Committee for Scientific Research (KBN, Poland) grant No. 2 T09A
098 15 and NSF-M. Sk³odowska-Curie Fund II Grant PAN/NSF-98-330 to Z. Jedliñski is acknowledged.
Corresponding author: Z. Jedliñski, Centre of Polymer Chemistry, Polish Academy of Sciences, M. Curie-
Sk³odowskiej 34, 41-800 Zabrze, Poland; phone: [phone]; fax: [phone];
e-mail: [e-mail]
Abbreviations: PHB, poly-(R)-3-hydroxybutanoate; OHB, oligo-(R)-3-hydroxybutanoate; poly-P, calcium
polyphosphate; Mw, weight average molecular weight; Mn, number average molecular weight; GPC, gel
permeation chromatography; ESI-MS, electrospray ionization-mass spectroscopy; 18-Crown-6,
1,4,10,13,16-hexaoxacyclooctadecane; 15-Crown-5, 1,4,7,10,13-pentaoxacyclopentadecane.
tention of chemists and biologists, and a lot of
attempts have been made to synthesize analogues
of natural PHB using various synthetic
methods.
D. Seebach and his associates have developed
an elegant method of PHB preparation
using step-by-step polycondensation of
(R)-3-hydroxybutanoic acid. However, this
procedure is very laborious and time-consuming
because protection and deprotection
of end groups of the monomer and intermediate
oligomers are necessary at each polycondensation
step [2, 3] (Scheme 1).
Another synthetic procedure was based on
ring-opening polymerization of -butyrolactone
(Scheme 2) using organometallic
coordinative initiators. However, the resulting
polymers exhibited very broad molecular
weight distribution and end groups which
were different from those found in natural
polymers present in living systems [4–7].
In this article we present the synthesis of
biomimetic analogues of natural PHB using
-butyrolactone as a monomer and supramolecular
complexes with alkali metals as catalysts.
MATERIALS AND METHODS
Materials. (S)--Butyrolactone (97.5% (S) +
2.5% (R) (gift from Central Research Laboratory,
Takasago International Corp.,
Hiratsuka, Japan) was purified as described
80 Z. Jedliñski and others 2000
Scheme 1. Synthesis of (R)-3-hydroxybutanoic acid tetrameter by multistep condensation reaction [3].
previously [8]. Potassium metal (Fluka) was
purified by washing with boiling toluene and
dried under vacuum. (R)-3-Hydroxybutanoic
acid sodium salt (Aldrich) was dried under reduced
pressure at 50C for 48 h. Penicillin G
potassium salt (Merck) was used as received.
THF was purified as described in ref. [9] and
then distilled over sodium-potassium alloy
just before use. 18-Crown-6 (Fluka) was purified
as described earlier [10]. 15-Crown-5
(Aldrich) was dried under vacuum at 40C for
10 h. Inorganic poly-P (type 65) was obtained
from Sigma. Buffers were ultrapure (> 99%)
(Aldrich). The lipid used was 1,2-dierucoylphosphatidylcholine
(di22:1 PC) (Avanti
Polar lipids).
Preparation of catalysts. The solution of
potassium supramolecular complex was obtained
by the contact of the potassium mirror
with THF solution of crown ether 18-crown-6
(0.1 mol/dm3) at 0C. After exactly 15 min the
resulting blue solution was filtered through a
coarse frit to the reactor (concentration of potassium
anions: [K–] = [18-crown-6] = 0.1 mol/
dm3). (R)-3-Hydroxybutanoic acid sodium
salt/15-crown-5 complex and penicillin G potassium
salt/18-crown-6 complex were prepared
similarly as described previously [10,
11].
Polymerization of (S)--butyrolactone.
(S)--Butyrolactone was polymerized in bulk
or in solution (THF or CHCl3), respectively,
under stirring in a previously flamed and argon-
purged glass reactor. The monomer and
solvent were added into the reactor containing
the required amount of initiator (potassium
ion pairs, (R)-3-hydroxybutanoic acid sodium
salt/15-crown-5 complex or penicillin G
potassium salt/18-crown-6 complex, respectively)
under dry argon atmosphere. The progress
of polymerization was measured by the
FT-IR technique (based on the comparison of
the band intensities at 1823 and 1740 cm–1
corresponding to absorption of carbonyl carbons
of monomer and polymer, respectively).
When polymerization was complete, ethyl
ether solution of HCl was added into the reactor
and after 10 min the polymer formed was
precipitated in hexane. Next the polymer was
redissolved in CHCl3, and the alkali metal
chloride/18-crown-6 complex was extracted
(five times) with water. Then the polymer was
precipitated in hexane, dried under vacuum
for 48 h, and analyzed by GPC, 1H NMR,
ESI-MS and optical rotation measurements.
The degree of isotacticity was determined by
the method described previously [11].
Preparation of PHB/poly-P complexes. A
chloroform solution of low molecular PHB
(Mn 1670, Mw/Mn 1.2 and a degree of
isotacticity of 94% as determined by 1HNMR)
was added to dry, pulverized poly-P and chloroform
was removed with a stream of purified
nitrogen gas. The mixture was heated in a microwave
oven (2 30 s). Chloroform was
added and the mixture was sonicated in a
Branson ultrasonication bath for 30 min at
4°C.
Reconstitution of PHB/poly-P channels
in lipid bilayer membranes was described
in detail previously [12]. An aliquot of a chloroform
solution of OHB19/23/poly-P complexes
was added to the phospholipid/cholesterol
mixture (5:1; w/w) in decane
(40 mg/cm3). The ratio of PHB to phospholipid
was < 1:10 000. After removal of the
chloroform by evaporation with a stream of
dry nitrogen, the solution was used to form a
bilayer across an aperture of about 200 mdiameter.
Analyses. 1H NMR spectra of obtained PHB
oligomers and polymers were recorded by using
a Varian VXR-300 spectrometer in CDCl3
with tetramethyl silane as the internal stan-
Vol. 47 Biomimetic poly-(R)-3-hydroxybutanoate 81
Scheme 2. Synthesis of poly--butyrolactone with
a coordinative catalyst
dard. FT-IR spectra were recorded using a
40A Bio-Rad spectrometer at room temperature.
GPC was performed at 30C, using a
Spectra Physics 8800 gel-permeation chromatograph
with two PL-gel packed columns
(103 Å and 500 Å). THF was used as the
eluent at a flow rate of 1mL/min. Polystyrene
standards with low polydispersity (PL-Lab.)
were used to generate a calibration curve.
Number average molecular weight Mn of the
obtained polymers was determined by GPC
and confirmed by the vapour pressure
osmometry technique in chloroform. Optical
rotation measurements were conducted in
CHCl3 using a Perkin-Elmer 141 polarimeter.
RESULTS AND DISCUSSION
Three initiators have been used for initiation
of (S)--butyrolactone polymerization.
The preparation of the first one was based
on discoveries of Dye [13] and Edwards [14]
concerning the dissolution of alkali metals:
potassium or sodium in an aprotic solvent,
such as THF, containing a macrocyclic organic
ligand e.g. 18-crown-6 or cryptand
[2.2.2]. The specific procedure (see Materials
and Methods) enabled the preparation of an
unique alkali metal supramolecular complex
forming in THF solution an alkali metal ion
pair, e.g. K+,L/K– (where L = 18-crown-6)
(Fig. 1).
Such alkali metal ion pairs are capable of
two electron transfer from the potassium anion
towards a suitable substrate, e.g.
-butyrolactone with formation of a respective
carbanion (Scheme 2). The strong tendency to
two electron transfer is due to the unusual oxidation
state of potassium anion bearing on its
outer s orbital two labile electrons shielded
from the positive potassium nucleus by inner
orbitals. Using S-enantiomer of -butyrolactone
as amonomer and potassium supramolecular
complex as catalyst, enolate carbanion is
formed as the first reactive intermediate
which induces polymerization, yielding
poly-(R)-3-hydroxybutanoate [15,16]. Direct
evidence for two electron transfer from the
supramolecular complex to the monomer is
provided by 39K NMR (Fig. 1). The resulting
biomimetic polyester has the structure similar
to native PHB produced in nature, except
for acetoxy-end-groups (Scheme 3) which are
formed instead of the hydroxyl ones typical
for natural PHB.
Considering the fact that even small structural
defects can change the bioactivity of a
biopolymer we have been looking for another
regioselective initiator which would be able to
produce poly-(R)-3-hydroxybutyrate bearing
82 Z. Jedliñski and others 2000
Figure 1. a)
39
K NMR of the potassium ion pair
with 18-crown-6 in THF solution before a reaction;
b)
39
KNMRof this solution after a reaction.
Scheme 3. Synthesis of
biomimetic PHB using potassium
supramolecular
complex as initiator.
only –OH and –COOH end groups typical for
natural PHB. It turned out that sodium salt of
(R)-3-hydroxybutanoic acid activated by
added crown ether can act as a very effective
initiator inducing polymerization of
(S)--butyrolactone. The hydroxybutanoate
anion of the initiator attacks the chiral carbon
atom of the monomer, as it is usual in
ring-opening reactions of -lactones induced
by carboxylate anions [17] (Scheme 4). The
structure of synthetic biomimetic PHB is
identical as that of the natural polymer.
The artificial model of a cell membrane was
prepared using biomimetic PHB with the calcium
polyphosphate (poly-P) complex incorporated
into lipid bilayers of 1,2-dierucoylphosphatidylcholine.
It was found that PHB
poly-P channels show high conductance for
Ca2+ and Na+ cations [12].
Thus the low molecular weight PHB-polymer
(19–20 monomer units) can be used effectively
for preparation of artificial ion channels
mimicking natural ones. The model of channels
proposed by Reusch [18] and depicted in
Fig. 2, contains two helices: the outer one containing
poly-(R)-3-hydroxybutanoate, complexed
by hydrogen bonding with the inner helix
of poly-P.
PHB polymers containing bioactive groups,
e.g. -lactame moieties characteristic for
-lactame antibiotics have also been prepared
[19] (Scheme 5).
Vol. 47 Biomimetic poly-(R)-3-hydroxybutanoate 83
Scheme 4. Synthesis of biomimetic
PHB using ((R)-3-hydroxybutanoic
acid sodium salt/15-crown-5) complex
as initiator.
Figure 2. Model of channels formed by the complex
of biomimetic low molecular PHB with calcium
polyphosphate.
Further studies on possible usefullness of
such polymers for preparation of drugs showing
prolonged activity are under way.
The authors are greatly indebted to Prof.
R.W. Lenz (Massachusetts University,
Amherst) and Prof. R.N. Reusch (Michigan
State University) for stimulating discussions.
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84 Z. Jedliñski and others 2000
Scheme 5. Synthesis
of biomimetic PHB
containing penicillin
G units.
11. Jedliñski, Z., Kurcok, P. & Lenz, R.W. (1998)
First facile synthesis of biomimetic poly-
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Vol. 47 Biomimetic poly-(R)-3-hydroxybutanoate 85