Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ENCODING SCHEME FOR SOLID PHASE CHEMICAL LIBRARIES
BACKGROUND OF THE INVENTION
The invention relates generally to the field of combinatorial chemistry,
and in particular to encoding schemes for solid phase chemical libraries. More
specifically, the invention relates to the production of constructs which have
different
physical characteristics to allow the constructs to be physically separated
into
different groups.
Recent trends in the area of research for novel chemical and especially
pharmacological agents have been concentrated on the preparation of so-called
"chemical libraries" as potential sources of new leads for drug discovery.
Chemical
libraries are intentionally created collections of differing molecules which
can be
prepared either synthetically or biosynthetically and screened for biological
activity in
a variety of formats. Examples of chemical libraries include libraries of
soluble
molecules; libraries of compounds tethered to resin beads, silica chips or
other solid
supports; or recombinant peptide libraries displayed on bacteriaphage or other
biological display vectors.
Of particular interest to the present invention are chemical libraries
which are tethered to individual solid supports, which typically take the form
of resin
beads. A variety of techniques have been proposed for making chemical
libraries
which utilize individual solid supports to which the compounds are tethered.
One
such method is the "discrete" method where solid supports are placed into
multiple
reaction vessels. Various chemicals are then synthesized onto the solid
supports
while the solid supports remain within the reaction vessels. After completing
the
synthesis process, the chemical compound on each solid support may be
identified
simply by identifying the reaction vessel from which the solid support was
removed.
Because of the need to maintain the solid supports within a given reaction
vessel, the
size of the resulting chemical library is limited by the number of reaction
vessels
used.
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In an attempt to greatly increase the size of a chemical library, the mix
and split technique was developed. In the mix and split method, solid supports
are
placed into individual reaction vessels and a first building block is
synthesized onto
each of the solid supports. Solid supports are then mixed together and
redistributed to
the reaction vessels where a second building block is synthesized onto the
solid
supports. The solid supports may once again be mixed and redistributed where
another building block may be synthesized onto the solid supports. This
process may
be repeated as many times as necessary. Examples of mix and split techniques
are
described generally in U.S. Patent No. 5,503,805, the complete disclosure of
which is
herein incorporated by reference.
As an example of split synthesis in the solid state synthesis of peptides,
a batch of resin supports (typically small resin beads) may be divided into n
fractions,
coupling a single monomer amino acid to each aliquot in a separate reaction,
and then
thoroughly mixing all of the resin particles together. Repeating this protocol
for a
total of x cycles can produce a stochastic collection of up toeometric
distribution.
Further, to ensure representation of the majority of possible ligan nX
different
molecules, as governed by a hypergds, a relatively large number of beads
should be
employed. A typical value may be about ten times as many beads as the desired
number of ligands.
Once a mix and split chemical library has been produced, the
compound may be cleaved from the solid supports and tested to determine if the
compound produces the desired result. If so, the particular compound needs to
be
identified. However, since the solid support was mixed and split one or more
times
during the synthesis process, identifying the compound on the solid support
can be
challenging.
As described in greater detail thereafter, some have proposed to
associate labels with the compounds as they are proceeding through their
combinatorial steps. For example, where the compounds are tethered to resin
beads,
prior art solutions to the problem have included attaching chemical identifier
tags to
the beads coincident with each block coupling step in the synthesis. The
determined
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properties of each tag then convey which building block was coupled in a
particular
step of the synthesis. The overall structure of a ligand on any bead may then
be
determined by reading the set of tags on that bead, in effect having encoded
the bead.
An alternative method for producing combinatorial libraries of
chemicals involves techniques utilized by both the discrete method and the mix
and
split method. According to this hybrid method, solid supports are placed at
discrete
locations and a set of chemicals are synthesized onto each of the solid
supports while
they remain within their discrete locations. A ligand code is also coupled to
each of
the solid supports, and may be used to identify the chemicals synthesized onto
their
solid supports while at their discrete locations. The solid supports are then
mixed and
split where still another chemical is synthesized onto each of the solid
supports. The
chemical compound on each of the solid supports may then be identified by
knowing
the position of the solid support when the last building block was added, and
by
reading the ligand code to determine the chemical compounds added while the
solid
supports were at their discrete locations. Such a technique is described
generally in
PCT International Application No. PCT/US97/05701, and in H. Mario Geysen, et
al.,
Isotope or Mass Encoding of Combinatorial Libraries, Chem. & Biol. Vol. III,
No. 8,
pp. 679-688, August 1996, the complete disclosures of which are herein
incorporated
by reference.
As previously mentioned, because the solid supports are combined
together and then redistributed into reaction vessels, there is a need to
identify the
components of the ligands as they are synthesized onto the solid supports. In
this
way, the chemical synthesis steps may be determined so that the final compound
synthesized onto the solid supports may be determined. A variety of encoding
schemes have been proposed to record the synthesis process. One such technique
is
the parallel encoding technique where the progressive assembly of tags is
performed
in conjunction with the construction of the ligand. The tags are used as a
binary code
to record the reaction history of each bead. The code can then be read
directly from a
single bead by electron capture capillary gas chromaphotography. Such a
process is
described generally in Michael H. J. Ohlmeyer, et al., Complex Synthetic
Chemical
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Libraries Indexed with Molecular Tags, Proc. Natl. Acad. Sci. USA, vol. 90,
pp.
10922-10926, December 1993, the complete disclosure of which is herein
incorporated by reference.
Another encoding strategy proposes the use of a microelectronic
device called a radio frequency memory tag. This tag may be embedded into a
solid
support and provided with a unique binary code. To read the code, the chip is
placed
near a computer interface transceiver, which causes the chip to power up, read
its
identification tag, and send a code to the transceiver in an RF pulse. Such a
technique
is described generally in A. W. Czarnik, Encoding Strategies and Combinatorial
Chemistry, Proc. Natl. Acad. Sci. USA, vol. 94, pp. 12738-12739, November
1997,
the complete disclosure of which is herein incorporated by reference.
The complexity surrounding combinatorial libraries is often increased
because of the requirement imposed by different chemists, which often prefer
different types of assays in order to determine which ligands produce a
positive result.
For example, depending on the chemist, the combinatorial library may need to
be
compatible with direct binding assays, lawn assays, solution assays, and the
like. As a
result, multiple libraries may need to be produced, which each include the
same set of
ligands but which are constructed using a different process so that each of
the libraries
is conducive with a different type of assay. The use of different types of
assays to
evaluate chemical libraries is described generally in Daniolos, A. et al.
Pigment Cells
Res., 3, 38-43 (1990); Jayawickreme, C. K., Proc. Natl. Acad. Sci. 91, 1614-
1618; and
Lam, Kit S., et al., "The 'One-Bead-One-Compound' Combinatorial Library
Method", Chem. Rev, 1997, 97, 411-448, the complete disclosures of which are
herein
incorporated by reference.
As is readily apparent, the building of multiple libraries with identical
ligands
is both costly and time consuming. Hence, it would be desirable to provide
ways to
construct a single library that may be separated into groups such that each
group is
suitable for an appropriate assay format. More specifically, it would be
desirable to
provide a way to identify the manner of attachment of a linking component so
that it
may be determined which process may be employed to test the particular
construct.
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In one aspect, it would be desirable to provide additional ways to separate
groups of
constructs to increase the number of possibilities for identifying various
aspects of the
constructs.
SUMMARY OF THE INVENTION
The invention provides exemplary chemical libraries, methods for
producing chemical libraries, and methods for evaluating chemical libraries.
In one
exemplary embodiment, a chemical library comprises a plurality of constructs
which
are separable into physically distinct groups. The constructs in each group
have at
least one common physical characteristic which is physically distinct from the
physical characteristics of the constructs in all other groups. In this
manner, the
constructs may easily be separated into different groups based upon their
common
physical characteristics.
Examples of physical characteristics which may be utilized include
size, density, geometry, color, magnetization, charge, refractive index, and
the like, as
well as those described in U.S. Patent No. 5,708,153, the disclosure of which
is herein
incorporated by reference. In one particular aspect, the physical
characteristics are
classifiable into categories. In this way, the category of at least one of the
groups may
be different from the other groups. As an example, one of the categories may
be size
and another one of the categories may be density. Hence, the chemical library
may
have constructs which have differing physical characteristics within the same
type
and/or physical characteristics of different types. In this way, the number of
possibilities for different physical characteristics may be greatly increased.
In another particular aspect, each construct comprises a solid support
to which are attached multiple components. Such components can include, for
example, a ligand component and at least one linking component. In some cases,
the
construct may also include one or more one ligand coding components.
Preferably,
the constructs of each group have linking components which have been assembled
in
essentially the same manner. In this way, the common physical characteristic
of each
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group is representative of the process by which the group is testable, i.e.,
by knowing
the manner of assembly of the linking components, one can determine the
particular
type of assay which should be employed to evaluate the ligand components. As
such,
the manner of assembly of the linking components of each group is preferably
unique
to each group. Once the constructs have been separated and tested, individual
constructs which tested positive may be decoded (if appropriate) to determine
the
ligand.
In one particular aspect, the ligand component is composed of three
different building blocks. Further, each ligand code component is readable to
determine two of the building blocks on each solid support. In this way, the
ligand
code may be employed to determine the first two building blocks which were
synthesized while the solid supports were placed at discrete locations. The
solid
supports may then be mixed and split where the third building block is
synthesized
onto the solid supports. As such, the third building block is known. Hence,
the
building blocks employed to produce the chemical composition may readily be
determined by evaluating the ligand code component, while the manner of
attaching
the ligand components may be determined based on the physical characteristics
of the
construct.
The invention further provides an exemplary method for producing a
chemical library. The method utilizes a plurality of solid support groups,
where each
group includes multiple solid supports which have at least one common physical
characteristic which is different from the physical characteristics of the
solid supports
of the other groups. The method proceeds by attaching at least one linking
component to each of the solid supports. The manner of attachment of the
linking
components is unique to each group as compared to the other groups. Further, a
ligand is synthesized onto each solid support such that each group of solid
supports
receives the same ligands. In this way, a chemical library is produced where
the
manner of attachment of the linking components may readily be identified.
Identification of the manner of attachment of the linking components is
advantageous
in that the process by which the group is testable to evaluate the ligand may
be
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determined simply by knowing the common physical characteristic of the group
to
which the solid support pertains. Optionally, one or more ligand coding
components
may also be attached. In such an event, a particular ligand may be identified
by
decoding the ligand component, typically after a tested construct has produced
a
positive result.
The physical characteristics by which the testable processes may be
identified include size, geometry, density, color, magnetization, charge,
refractive
index, and the like. As previously described, the physical characteristics may
be
classifiable into categories so that the physical characteristics may differ
within a
given category or across certain categories. In one particular aspect, the
processes by
which the groups may be tested include direct binding assays, lawn assays,
solution
assays, and the like.
In one particular step, multiple solid supports are placed into
physically discrete locations prior to the synthesizing step. Each of the
locations is
provided with at least one solid support from each of the groups. With this
arrangement, one or more building blocks may be synthesized onto each solid
support
while the solid supports are at the discrete locations. With this arrangement,
the
ligand coding component is preferably representative of the building block(s).
Following synthesis of the building block(s), the solid supports are
preferably mixed
and allocated into a plurality of vessels where another building block is
synthesized
on each of the solid supports. In this manner, the ligand may be identified by
utilizing
the ligand code to determine the initial building block(s). Further, the
process by
which each group is testable may be determined simply by determining the
common
physical characteristics of each of the groups. In this way, the solid
supports may be
separated into groups where each group is tested using a different assay. If a
positive
result is obtained, the ligand may be determined by reading the ligand code.
The invention further provides an exemplary method for evaluating a
chemical library. According to the method, a plurality of constructs are
provided
which are typed by at least one common physical characteristic. The constructs
have
been separated into groups based on their type. Following separation, each of
the
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groups may be evaluated, with each group containing information which will
assist in
the evaluation process. For example, each group may require the performance of
a
different assay in order to evaluate the ligand. More specifically, the
constructs of
one group may have linking components which have been assembled in essentially
the same manner so that the common physical characteristic of each group is
representative of the process by which the group is testable.
In one particular aspect, the physical characteristic is density. In this
way, the constructs may be separated by sequentially placing the constructs
within
fluids having different densities and removing the constructs that rise to the
top of
each fluid. As another example, at least one of the physical characteristics
may be
size. With this construction, the constructs may be sieved or agitated to
permit the
larger sized constructs to rise to the top of the remaining constructs. The
larger size
constructs may then be picked from the collection, preferably utilizing a
picking
device which can distinguish based on size.
In another embodiment, the invention provides an exemplary chemical
library system which comprises at least two different chemical libraries. Each
chemical library comprises a plurality of solid supports onto which at least
two
building blocks are coupled. The solid supports of each library have a unique
physical characteristic common to the library which allows the library to
which each
solid support belongs to be identified. In this way, the libraries may be
combined to
facilitate testing. When desired, the library from which a particular solid
support
originated may be determined simply by evaluating its physical characteristic.
The
physical characteristics of the solid supports are preferably selected from a
group
consisting of size, geometry, density, color, magnetization, charge, and
refractive
index.
The invention further provides an exemplary method for evaluating
two or more different chemical libraries. According to the method, at least
two
different chemical libraries are provided, with each library comprising a
plurality of
solid supports onto which at least two building blocks are coupled. Further,
the solid
supports of each library have a unique physical characteristic common to the
library.
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The two libraries are combined together to form a combined library, and the
combined library is tested for positive outcomes. If any positive outcomes are
observed, the library or libraries to which those solid supports belong are
identified
based on the physical characteristic of the solid supports.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. lA is a schematic diagram of four groups of constructs which
differ in size according to the invention.
Fig. 1B illustrates four groups of constructs which differ in density
according to the invention.
Fig. 1 C illustrates four groups of constructs, at least some of which
differ in density, shape, and size according to the invention.
Fig. 2A is a schematic diagram of an exemplary construct according to
the invention.
Fig. 2B is a schematic diagram of an alternative construct according to
the invention.
Fig. 3 is a flow chart of an exemplary method for evaluating a
chemical library according to the invention.
Fig. 4 is a schematic diagram of a process for producing a chemical
library according to the invention.
Fig. 4A is an enlarged view of a discrete well of Fig. 4 taken along
lines A-A.
Fig. 4B is an enlarged view of a reaction vessel of Fig. 4 taken along
line B-B.
Fig. 5 is a schematic diagram illustrating the combination and
subsequent evaluation of two or more different libraries according to the
invention.
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DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENTS
A "construct" as used herein, is a covalently bonded entity comprising,
in any combination, some type of solid support, one or more linking
components, one
or more ligands, and optionally one or more ligand coding components.
A "ligand coding component" is a component which may be linked to
a solid support and which contains information about at least one of the
chemicals
used to construct a ligand which is also linked to the solid support.
A "ligand" is a chemical reaction product of interest. A ligand can be
part of a larger construct, where the ultimate goal will be to identify and/or
cleave the
ligand apart from the rest of the construct.
A "linking component" is a covalent bond or a molecular moiety that is
suitable for linking two portions of a construct together.
A "solid support" is one or more materials upon which combinatorial
chemistry synthesis can be performed, including beads, solid surfaces, solid
substrates, particles, pellets, discs, capillaries, hollow fibers, needles,
solid fibers,
cellulose beads, pore glass beads, silica gels, polystyrene beads optionally
crosslinked
with divinylbenzene, grafted copoly beads, polyacrylamide beads, latex beads,
dimethylacrylamide beads, optionally cross-linked N, N'-bis-acryloyl ethylene
diamine, glass particles coated with a hydrophobic polymer, fullerenes and
soluble
supports, such as low molecular weight, noncrosslinked polystyrene.
The invention provides exemplary constructs having different physical
characteristics which allows the constructs to be separated into different
groups. The
physical characteristics by which the groups may be separated facilitate the
identification of a particular feature or aspect of the constructs within a
given group.
For instance, the common physical characteristics may be employed to identify
the
process by which the group is testable when screening the ligands. As another
example, the common physical characteristic of a group may be used to identify
a
particular building block used in a synthesis process. As yet another example,
the
common physical characteristic may be employed to identify a particular
library to
which the construct belongs after two or more libraries have been combined.
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The constructs of the invention may be constructed to have a wide
variety of physical characteristics which allow the constructs to be separated
into
groups having at least one common physical characteristic. For example,
physical
characteristics which may be employed include size, density, geometry, color,
magnetization, charge, refractive index, and the like. Conveniently, the
physical
characteristics may be categorized into types. For example, one type may be
size and
another type may be density. The invention may utilize differences within each
type
or across different types. For example, constructs may be constructed to have
various
sizes so that the constructs may be separated into the different groups based
on their
size. As another example, some of the constructs may be differently sized
while other
constructs may have a different geometry. Hence, a variety of combinations of
physical characteristics may be provided based on differences within a given
type
and/or across various types.
Examples of different physical characteristics which may be utilized
with the invention are illustrated in Figs. lA-1C. In Fig. lA, the solid
supports are
grouped into four groups, with each group having a different size. A variety
of
techniques may then be employed to separate the constructs into different
groups. For
example, different size sieves may be employed to filter the different size
constructs.
As another alternative, the constructs may be agitated so that the larger size
constructs
rise to the top. A bead picking apparatus, such as the one described in U.S.
Patent
Application Serial No. 09/240,758, filed January 29, 1999, the complete
disclosure of
which is herein incorporated by reference, may be utilized to remove the
largest
constructs. The constructs may then again be agitated and the process repeated
for
each of the groups. Other possible separation techniques include the use of
magnets,
fluorescence activated cells sorters, and other separation techniques known in
the art.
An alternative scheme for separating constructs is illustrated in Fig.
1B. According to this scheme, each group of constructs has a solid support
with a
different density as represented by reference symbols pl-p4. To separate the
constructs into groups, the constructs may be placed into a solution having a
given
density such that the group with the lowest density rises to the top of the
solution.
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These constructs may then be skimmed from the solution. The density of the
solution
is then increased until the group with the next largest density rises to the
top of the
solution. This process is then repeated until all the groups have been
separated.
Fig. 1 C illustrates another alternative for separating the constructs into
different groups. In Fig. 1 C, the constructs are categorized into different
types. For
example, groups l and 2 are classified by density, group 3 is classified by
shape, and
group 4 is classified by size. Further, the constructs within groups 1 and 2
differ
within the same type. More specifically, group 1 has a density that is
different than
group 2. A variety of techniques may then be employed to separate the
constructs
into their respective groups. For example, an optical detector may be employed
to
determine differences in size and shape. Differences in density may be
detected using
different density of solutions as previously described. Agitation techniques
may also
be employed as previously described.
One advantage of the categorizing the solid supports into groups is that
each group may be tested utilizing a different assay. In this way, one library
may be
produced which may be utilized with a variety of assays so that multiple
libraries do
not need to be constructed. This is best accomplished by assigning a physical
characteristic to each group which is representative of the manner in which
the linking
components of the construct are assembled onto the solid support. To
illustrate this
principle, a typical construct 10 is shown schematically in Fig. 2A. Construct
10
includes a solid support 12 to which is coupled a linking component 14, a
ligand
coding component 16 and a ligand component 18. Although shown with only one
linking component 14, it will be appreciated that other numbers and
arrangements of
linking components may be provided. For example, a linking component may be
provided between ligand coding component 16 and ligand component 18. Such a
construct is described in, for example, PCT International Application No.
PCT/US97/05701, the complete disclosure of which is herein incorporated by
reference. Another example of a construct 11 is shown in Fig. 2B and includes
a solid
support 12' and a pair of linking components 13 which are used to attach a
ligand
coding component 15 and a ligand 17. Such a construct is described in, for
example,
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U.S. Patent No. 5,770,358, the complete disclosure of which is herein
incorporated by
reference. Further, it will be appreciated that other types of constructs
exist which
may be utilized with the invention. For convenience of discussion, reference
will be
made hereinafter to construct 10.
Depending on the manner of assembly of constructs 10, and in
particular, depending on the number, type and arrangement of the linking
components, a different assay will need to be employed in order to screen the
ligand
component 18 following synthesis. For example, direct binding assays, lawn
assays,
solution assays, and the like all employ different types and/or arrangements
of linking
components as described generally in Daniolos, A. et al. Pigment Cells Res.,
3, 38-43
(1990); Jayawickreme, C. K., Proc. Natl. Acad. Sci. 91, 1614-1618; and Lam,
Kit S.,
et al., "The 'One-Bead-One-Compound' Combinatorial Library Method", Chem. Rev,
1997, 97, 411-448, previously incorporated by reference. With lawn assays,
synthesized beads in an agarose solution are typically poured onto plates
containing
cells, such as melanophore cells. After the agarose solidifies, the plates are
exposed
to UV light and scanned. Individual beads above responding areas may then be
identified using a stereo microscope and removed. With direct binding assays,
a
bound target is detected either by direct visualization, e.g. a color target,
or indirectly
by using a reporter group such as an enzyme, a radionuclide, a fluorescent
probe, or a
color dye covalently attached to a target. For solutions assays, the ligands
are cleaved
from the solid supports into solution phase where biological assays can take
plate.
Such assays can include, for example, competitive receptor binding assays with
radiolabeled ligands, various enzymatic assays, cell-based signal transduction
assays,
antibacterial assays, antiviral assays, and anticancer assays.
Typically, the linking and ligand coding components are attached to
solid support 12 prior to a synthesis process. In this way, solid support 12
may be
provided with a unique physical characteristic which may be used to identify
the
manner of attachment of the linking components. Once the solid support has
been
provided with the appropriate ligand coding component and linking component,
the
synthesis process proceeds to synthesize ligand component 18 to the solid
support.
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As described in greater detail hereinafter, it is preferred to synthesize the
same set of
ligand components to each group of solid support so that each group may be
independently evaluated.
Referring now to Fig. 3, an exemplary method for processing the
constructs will be described. As shown in step 20, multiple types of
constructs which
each have the same set of ligands is produced in a manner similar to that just
described. In step 22, the constructs are physically separated into groups
based on the
types, i.e., based on the common physical characteristic that is unique to the
group.
Once the constructs have been physically separated, an assay is selected for
each of
the groups. The type of assay may be determined based on the physical
characteristic
that is common to the group as shown in step 24. In step 26, the selected
assays are
performed on each group of constructs to screen the ligands. Optionally, as
shown in
step 27, the constructs which produce positive results may be decoded to
identify the
ligand.
Referring now to Fig. 4, one exemplary way to construct a chemical
library which has groups of constructs that are defined by different physical
characteristics will be described. However, as previously described, it will
be
appreciated that the separating techniques of the invention may be used with a
wide
variety of constructs. The process of Fig. 4 is somewhat related to the
techniques
described in PCT International Application No. PCT/LTS97/05701, previously
incorporated by reference, and in H. Mario Geysen, et al., Isotope or Mass
Encoding
of Combinatorial Libraries, Chem. & Biol. Vol. III, No. 8, pp. 679-688, August
1996,
previously incorporated by reference. The process shown in Fig. 4 employs the
use of
a plate 28 having a plurality of wells 30. As shown, wells 30 are arranged in
ten rows
and ten columns to form a total of 100 wells. As best shown in Fig. 4A, a
plurality of
solid supports 32 are placed within each of the wells. Each of solid supports
32
preferably already includes one or more linking components and one or more
ligand
coding components. The manner of attachment of the linking components is
identified by a physical characteristic of the solid support. As shown in Fig.
4A, well
30 includes solid supports 32 having four different densities as identified by
reference
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numerals pl-p4. Another group of solid supports has a size which is
significantly
larger than the other solid supports.
The size of solid supports 32 may vary depending on the particular
application, and may range in size from about 1 ~m to about 500 Vim. Each well
30
preferably includes enough solid supports from each group to ensure that a
complete
set of ligands is produced on each of the groups.
Referring back to Fig. 4, each column of wells 30 is referenced by a
reference numeral Al-Alo, and each of the ten rows is identified by a
reference
numeral B~-Blo. These reference numerals are provided schematically to show
the
particular chemicals that are introduced into each of the wells. For example,
in the
first well, each of the solid supports will receive AI and B1 as the first two
building
blocks. In practice, a table will preferably be maintained indicating which
chemicals
are provided into each of the wells.
After the first two building blocks have been synthesized onto the solid
supports, the solid supports are transferred to a pool 34 where they are
thoroughly
mixed. Following mixing, the solid supports within pool 34 are generally
equally
distributed into ten reaction vessels 36. Each of reaction vessels 36 is
schematically
marked with a reference numeral C1 through Clo. These reference numerals
indicate
the third building block which is added to the associated reaction vessel 36.
As
shown in Fig. 4B, because the number of reaction vessels 36 is one-tenth the
number
of wells 30, each reaction vessel will receive approximately ten times the
number of
solid supports 32. Although shown with a ten by ten starting matrix and a one
by ten
ending matrix, it will be appreciated that a variety of other sized matrices
may be
employed. For example, the ending matrix may also be a ten by ten matrix.
Following synthesis of the third building block onto each of the solid
supports, the solid supports are ready to be screened to determine any
positive results.
The type of screening to be performed will depend upon which group the
construct
belongs. Hence, prior to screening the solid supports within each of reaction
vessels
36, the solid supports will be physically separated into groups based on the
common
physical characteristic of each group. When separating solid supports 32 into
their
CA 02367541 2001-10-04
WO 00/61281 PCT/US00/09093
respective groups, the association of-solid supports 32 relative to their
reaction vessel
36 will be maintained so that the last building block is still identifiable.
One exemplary way to separate solid supports 32 into their different
categories is first to agitate reaction vessels 36 and then utilize a bead
picker to
remove the larger size solid supports which will rise to the top of the
remaining
constructs. A solution may then be introduced into each of reaction vessels 36
to
cause the least dense constructs to rise to the top of the fluid. These may be
skimmed
from the top and the density of the solution increased to allow the next of
constructs
to rise to the top. This process is repeated until all of the constructs are
separated into
groups.
Each of the groups may then be screened using assays that are suitable
for the particular group. If a positive result is observed, the ligand coding
component
on the solid support may be used to identify the first two building blocks,
with the
third building block being determined based upon the reaction vessel 36 from
which it
1 S was removed. In this way, the ligand may easily be identified using
techniques
known in the art.
Another application of the invention is the ability to combine two or
more different libraries to make the next step in a process more efficient,
while still
providing the ability to identify the libraries from which any given construct
originated. For example, two or more libraries may be combined prior to
screening to
make the screening process more efficient as illustrated in Fig. 5.
The process begins by providing two or more different libraries, with
libraries A and N being shown for convenience of illustration. The manner in
which
the libraries differ may greatly vary. For example, the libraries may vary in
that all of
the building blocks and/or chemistries in one library are different from
another
library. As another example, the libraries may differ in that they were
created at
different times. As yet another example, the ligand coding assignments may
differ
between the libraries. As still another example, the libraries may differ
except for
common subsets of ligands within the libraries.
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As shown in step 50, all of the libraries are combined and mixed. As
shown in step 52, the entire library is then screened for positive outcomes.
If one or
more positive outcomes are observed, the physical characteristics of the
positively
tested constructs are evaluated to determine the library from which the
constructs
originated as shown in step 54. That particular library may then be
individually
tested. In this way, one initial screening may be performed with multiple
libraries to
reduce the time and effort employed to screen large quantities of constructs.
The invention has now been described in detail for purposes of clarity
of understanding. However, it will be appreciated that certain changes and
modifications may be practiced within the scope of the dependent 'claims.
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