Covalent modifications to improve solubility of sparingly soluble substrates

I am looking for some covalent modifications that can be done to
either diphenylacetylene(DPA) or biphenyl (target substrates in our
research) to increase their aqueous solubility in E.coli growth
system.. So far, I have modified biphenyl to sulfonatedbiphenyl
(obtained commercially as biphenylsulfonic acid). However, due to
larger polarity of sulfonic group, the molecule as a whole is unable
to enter the inner part of the cell. Currently, I am working with
surfactants to enhance the solubility of DPA and also aid in their
transport.

Could you suggest some me some substrate covalent modifications to
biphenyl. Thankyou for your time.

sweetysom <[Only registered users see links. ]> said:

Attach glycine or alanine (several protected forms of biphenylalanine
are commercially available). Now you can attach various additional
peptide residues to affect targetting, transport properties, etc.

Attach a polyether (both 2- and 4-biphenylmethanol are commercially
available, or could attach as a sulfonate ester to commercially
available biphenyl-4-SO2Cl).

dan

--
Daniel Macks
[Only registered users see links. ]
[Only registered users see links. ]

[Only registered users see links. ] (sweetysom) wrote:


There are lots and lots of things you could attach. Most polar
moieties will improve aqueous solubility. But there is a tradeoff:
high polarity / low clogP / ionization, which act to increase
solubility, are also associated with decreased lipid bilayer
permeability (as you discovered with the sulfonate derivative). So
you have to play a balancing act. Usually the "sweet spot" between
adequate solubility and membrane permeability can only be determined
empirically. I would suggest looking at substitution with amino
groups (can be done in two steps via nitration and reduction) or
carboxylic acid(s) (commercially available).

Steve Turner

Real address contains worldnet instead of spamnet

Steve Turner <[Only registered users see links. ].net> wrote in message news:<[Only registered users see links. ]>. ..

Thankyou very much. I missed one point to be mentioned. The final
product after biocatalysis is Hydroxybiphenyl (HBP) from biphenyl. Any
modification made to biphenyl should also allow me to remove the
attachment at the end and get the desired product, HBP. As in the case
with sulfonation, although the product after biocatalysis is
Hydroxysulfonic biphenyl, it is easy to desulfonate. So is it possible
with nitration or reduction. If so, can u mention any references in
this case or references for covalent modification.

Regards,
Sweetysom

"Daniel E. Macks" <[Only registered users see links. ]> wrote in message news:<[Only registered users see links. ]>...

Thankyou very much. My final desired product being Hydroxy biphenyl
(HBP) from biphenyl, is it possible to remove the attachments that you
mentioned and get the desired product. As in the case of sulfonation,
the sulfonated hydroxy product can be desulfonated and the final
product can be obtained. Can you mention some references in this case
or for covalent modifications?

Regards,
Sweetysom

[Only registered users see links. ] (sweetysom) wrote:


So the overall goal is an biocatalyic method of producing
hydroxybiphenyl on a commercial scale??? I think maybe I'd look at
chemical methods.

An aromatic amine (aniline) function can be removed by diazotization
and reduction of the resulting diazonium salt. These types of
reactions can range from excellent to poor, depending on substrate.

Steve Turner

Real address contains worldnet instead of spamnet

Yes. The best solubilizing groups to get the molecule into cells are
amines. (Primary, secondary, tertiary - they all work) But stay away
from amides (-CONH2)

The trouble is: once you make such a modification, you are also
changing the other biological and chemical properties of the molecule
a great deal.


Steve Turner <[Only registered users see links. ].net> wrote in message news:<[Only registered users see links. ]>. ..

[Only registered users see links. ] (Muhammar) wrote in message news:<a6cffac9.0402011936.335425e@posting.google.c om>...

I thank all of you for your guidance. To get a good idea let me put my
project as follows:

The main aim of this project is to synthesize meta hydroxylated
isomers of biphenyl (BP) or diphenylacetylene (DPA). SO the final
products are m-HBP (hydroxybiphenyl) or m-HDPA
(hydroxydiphenylacetylene) depending on the product. These are known
to have very important application in aerospace applications. Chemical
methods are not desirable as they will not yield regiospecific isomer.
As mentioned earlier, the aqueous solubility of both these compounds
(BP or DPA) is very low, resulting in low biocatalysis rates. The
biocatalysis rates are found to be a function of substrate
concentration and enzyme concentration. Toluene/benzene-4-
monooxygenase (Tb4m) is used in this case. Initilly experiments were
done with Pseudomonas Aeruginosa strains. However, E.coli was chosen
later to obtain overexpression.
Tb4m enzyme is an intracellular multicomponent enzyme. Cannot be
isolated as it will be deactivated outside the cell. But the enzyme
concentration within the whole cell can be increased via
overexpression.
Sulfonation of biphenyl lead to increased solubility, however, was not
penetrable through the cell membrane.
Currently I am using variuos surfactants to increase the solubility of
DPA, which would increase the biocatalysis rates.
I am also looking for different alternatives like covalent
modifications. Depending on your suggestions I will look into further
details. I would appreciate if you could throw more light on the over
all project.

Thanking you.
-Sweetysom

I am sorry to tel you that your project looks like utter waste of
time. Of course biphenyl would be a very cheap starting material if
the biology would work.

But, even in your ideal case - is it not the poblem of all
fermentation processes that you end-up with a rich broth which has
only few hundreds miligrams of product per liter and you have to
isolate your product from such a soup? Kind of defeats the purpose -
if you want to make cheaply large quantiuties of the stuff. Tell you
prof that he is guilty of wishful thinking.

Contrary to your statement, there is plenty of good synthetic methods
available and some of them can be even done in one-pot experiment.
Besides, how much is the aerospace willing to pay? If it is >$50/kg,
than I am sure synthetic chemistry is far better alternative than
fermentation.

My guess is that your prof has isolated this bacterial enzymatic
system and is desperate to demonstrate that his research has any
practical value.
But from engineering point of view, one should start with a resonable
method and only try a funky one (like your bacteria stuff) when there
in no other reasonable alternative.



[Only registered users see links. ] (sweetysom) wrote in message news:<53b2f17c.0402021013.5126153b@posting.google. com>...

[Only registered users see links. ] (Muhammar) wrote in message news:<a6cffac9.0402021920.73c2beb3@posting.google. com>...

I thankyou for your valuable suggestion and time. It does make some
sense. However, I believe synthesising a meta - isomer is very
difficult via normal chemical methods and hence is the present
Biocatalytic method.

Could you throw more light on the variuos synthetic methods?