Method and substrate for performing multiple sequential reactions on a matrix

• US 6,015,880 A
• Filed: 03/16/1994
• Issued: 01/18/2000
• Est. Priority Date: 03/16/1994
• Status: Expired due to Fees

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Gamble, Ronald C., Theriault, Thomas P., Baldeschwieler, John D.
• Primary Examiner(s): Marschel, Ardin H.
• Application Number:
  US08/213,857
• Time in Patent Office: 2,134 Days
• Field of Search: 435/6, 435/7.1, 435/7.2, 435/7.92, 435/287, 435/288, 435/289, 435/290, 435/291, 435/296, 435/808, 435/810, 436/501, 436/63, 530/300, 530/333, 530/334, 530/335, 530/344, 530/350, 536/22.1, 536/23.1, 536/24.3-24.33, 536/25.3, 536/25.31, 536/25.4, 935/77, 935/78, 935/88
• US Class Current: 530/333
• CPC Class Codes: B01J 19/0046 Sequential or parallel reactions, e.g. for the synthesis of polypeptides or polynucleotides; Apparatus and devices for combinatorial chemistry or for making molecular arrays synthesis methods per se C40B50/00
• CPC Class Codes: B01J 2219/00369 in multiple or parallel arrangements
• CPC Class Codes: B01J 2219/00378 Piezoelectric or ink jet dispensers
• CPC Class Codes: B01J 2219/00475 Sheets
• CPC Class Codes: B01J 2219/00513 Essentially linear supports
• CPC Class Codes: B01J 2219/00527 Sheets
• CPC Class Codes: B01J 2219/00585 Parallel processes
• CPC Class Codes: B01J 2219/0059 Sequential processes
• CPC Class Codes: B01J 2219/00596 Solid-phase processes
• CPC Class Codes: B01J 2219/00605 the compounds being directly bound or immobilised to solid supports
• CPC Class Codes: B01J 2219/0061 The surface being organic
• CPC Class Codes: B01J 2219/00612 the surface being inorganic
• CPC Class Codes: B01J 2219/00621 by physical means, e.g. trenches, raised areas
• CPC Class Codes: B01J 2219/00626 Covalent
• CPC Class Codes: B01J 2219/00637 by coating it with another layer
• CPC Class Codes: B01J 2219/00641 the porous medium being continuous, e.g. porous oxide substrates
• CPC Class Codes: B01J 2219/00659 Two-dimensional arrays
• CPC Class Codes: B01J 2219/00675 In-situ synthesis on the substrate
• CPC Class Codes: B01J 2219/0068 Means for controlling the apparatus of the process
• CPC Class Codes: B01J 2219/00722 Nucleotides
• CPC Class Codes: B01J 2219/00725 : Peptides
• CPC Class Codes: B82Y 30/00 : Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C07H 21/00 : Compounds containing two or more mononucleotide units having separate phosphate or polyphosphate groups linked by saccharide radicals of nucleoside groups, e.g. nucleic acids
• CPC Class Codes: C07K 1/042 : characterised by the nature of the carrier
• CPC Class Codes: C07K 1/047 : Simultaneous synthesis of different peptide species; Peptide libraries
• CPC Class Codes: C40B 40/06 : Libraries containing nucleotides or polynucleotides, or derivatives thereof
• CPC Class Codes: C40B 40/10 : Libraries containing peptides or polypeptides, or derivatives thereof
• CPC Class Codes: C40B 50/14 : Solid phase synthesis, i.e. wherein one or more library building blocks are bound to a solid support during library creation; Particular methods of cleavage from the solid support
• CPC Class Codes: C40B 60/14 : for creating libraries

Abstract

A method and apparatus are provided for preparing a substrate upon which is located microdrop-sized loci at which chemical compounds are synthesized or diagnostic tests are conducted. The loci are formed by applying microdrops from a dispenser from which a microdrop is pulse fed onto the surface of the substrate.

Claims

1. A method of step-by-step synthesis of an array of different chemical compounds at microdrop-sized loci, where each compound is covalently attached to or beneath the surface of an undifferentiated substrate comprising the steps of:

(a) applying through a single jet of a multiple jet reagent dispenser at least one microdrop of a first reagent in liquid form to a loci on said surface, wherein said undifferentiated substrate is a porous material comprising a sheet having internal straight, essentially parallel pores, and is chemically prepared to react with said first reagent to covalently attach said reagent to said undifferentiated substrate;

(b) displacing said multiple jet reagent dispenser relative to said surface, or the surface with respect to said multiple jet reagent dispenser, and applying at least one microdrop containing either the first reagent or a second reagent from a different dispenser jet to a second loci on said surface wherein said substrate is chemically prepared to react with said reagent to covalently attach said reagent to said substrate;

(c) optionally repeating step (b) at least one time using either said first reagent, said second reagent, or different reagents in liquid form from different dispenser jets wherein each of said reagents covalently attaches to said substrate to form covalently attached compounds;

(d) washing said substrate to remove unattached reagents;

(e) modifying said attached reagents;

(f) repeating steps (a) through (e) with the same or different reagents at various loci on the substrate until the synthesis of different chemical compounds at each of at least 20 said loci is completed; and

(g) optionally removing the attached compounds at said loci from said substrate, wherein said optional removing is performed in a selective or a non-selective manner.

3. A method according to claim 1 or 2 wherein said porous material comprises paper.

2. A method of step-by-step synthesis of an array of different chemical compounds at discrete microdrop-sized loci, where each compound is covalently attached to or beneath the surface of an undifferentiated substrate comprising the steps of:

(a) applying through a single jet of a multiple jet reagent dispenser at least one microdrop of a first reagent in liquid form to said surface of said undifferentiated substrate at the first locus, wherein said substrate is a porous material comprising a sheet having internal straight, essentially parallel pores;

(b) displacing the multiple jet reagent dispenser relative to said surface and applying through a second jet of said multiple jet reagent dispenser a second reagent to the first locus to form a mixture of reagents at the first locus wherein said substrate is chemically prepared to react with said mixture to covalently attach one or more of said reagents to said substrate at the first locus;

(c) optionally repeating steps (a) and (b) at additional microdrop sized loci of said surface where the same mixture of reagents or a different mixture of reagents are formed at each locus, wherein said reagent is dispensed from a different jet of said multiple jet reagent dispenser;

(d) washing said substrate to remove the excess reagents;

(e) modifying said attached reagents;

(f) repeating steps (a) through (e) with the same or different reagents at various loci on the substrate until the synthesis of different chemical compounds at each of at least 20 said loci is completed; and

(g) optionally removing the attached compounds at said loci from said substrate, wherein said optional removing is performed in a selective or a non-selective manner.

4. A method of step-by-step synthesis of an array of different chemical compounds at microdrop-sized loci, where each compound is covalently attached to or beneath the surface of an undifferentiated substrate, wherein said substrate comprises a porous material, comprising the steps of:

(a) applying through a single jet of a multiple jet reagent dispenser at least one microdrop of a first reagent in liquid form to a loci on said surface, wherein said undifferentiated substrate is chemically prepared to react with said first reagent to covalently attach said reagent to said undifferentiated substrate;

(b) displacing said multiple jet reagent dispenser relative to said surface, or the surface with respect to said multiple jet reagent dispenser, and applying at least one microdrop containing either the first reagent or a second reagent from a different dispenser jet to a second loci on said surface wherein said substrate is chemically prepared to react with said reagent to covalently attach said reagent to said substrate;

(c) optionally repeating step (b) at least one time using either said first reagent, said second reagent, or different reagents in liquid form from different dispenser jets wherein each of said reagents covalently attaches to said substrate to form covalently attached compounds, and wherein said reagents in said microdrops comprise protected or unprotected amino acids, thereby forming polypeptides attached at said loci;

(d) washing said substrate to remove unattached reagents;

(e) modifying said attached reagents;

(f) repeating steps (a) through (e) with the same or different reagents at various loci on the substrate until the synthesis of polypeptides at each of at least 20 said loci is completed; and

(g) optionally removing the attached compounds at said loci from said substrate, wherein said optional removing is performed in a selective or a non-selective manner.

6. A method according to claim 4 or 5 wherein said porous material comprises paper.

7. A method according to claim 4 or 5 wherein said porous material comprises a sheet having internal straight, essentially parallel pores.

5. A method of step-by-step synthesis of an array of different chemical compounds at microdrop-sized loci, where each compound is covalently attached to or beneath the surface of an undifferentiated substrate, wherein said substrate comprises a porous material comprising the steps of:

(a) applying through a single jet of a multiple jet reagent dispenser at least one microdrop of a first reagent in liquid form to said surface at the first locus of said undifferentiated substrate;

(b) displacing the multiple jet reagent dispenser relative to said surface and applying through a second jet of said multiple jet reagent dispenser a second reagent to the first locus of said undifferentiated substrate to form a mixture of reagents at the first locus wherein said undifferentiated substrate is chemically prepared to react with said mixture to covalently attach one or more of said reagents to said undifferentiated substrate at the fist locus;

(c) optionally repeating steps (a) and (b) at additional microdrop sized loci of said surface where the same mixture of reagents or a different mixture of reagents are formed at each locus, wherein said reagent is dispensed from a different jet of said multiple jet reagent dispenser, and wherein said reagents in said microdrops comprise protected or unprotected amino acids, thereby forming polypeptides attached at said loci;

(d) washing said substrate to remove the excess reagents;

(e) modifying said attached reagents;

(f) repeating steps (a) through (e) with the same or different reagents at various loci on the substrate until the synthesis of polypeptides at each of at least 20 said loci is completed; and

(g) optionally removing the attached compounds at said loci from said substrate, wherein said optional removing is performed in a selective or a non-selective manner.

8. A method of step-by-step synthesis of an array of different chemical compounds at microdrop-sized loci, where each compound is covalently attached to or beneath the surface of a substrate, wherein said substrate comprises a porous material, comprising the steps of:

(a) applying through a single jet of a multiple jet reagent dispenser at least one microdrop of a first reagent in liquid form to a loci on said surface, wherein said substrate is chemically prepared to react with said first reagent to covalently attach said reagent to said substrate;

(b) displacing said multiple jet reagent dispenser relative to said surface, or the surface with respect to said multiple jet reagent dispenser, and applying at least one microdrop containing either the first reagent or a second reagent from a different dispenser jet to a second loci on said surface wherein said substrate is chemically prepared to react with said reagent to covalently attach said reagent to said substrate;

(c) optionally repeating step (b) at least one time using either said first reagent, said second reagent, or different reagents in liquid form from different dispenser jets wherein each of said reagents covalently attaches to said substrate to form covalently attached compounds, and wherein said reagents in said microdrops comprise protected or unprotected nucleotides, thereby forming oligonucleotides attached at said loci;

(d) washing said substrate to remove unattached reagents;

(e) modifying said attached reagents;

(f) repeating steps (a) through (e) with the same or different reagents at various loci on the substrate until the synthesis of oligonucleotides at each of at least 20 said loci is completed;

(g) optionally removing the attached compounds at said loci from said substrate, wherein said optional removing is performed in a selective or a non-selective manner, then amplifying said oligonucleotides by polymerase chain reaction amplification.

10. A method according to claim 8 or 9 wherein said porous material comprises paper.

11. A method according to claim 8 or 9 wherein said porous material comprises a sheet having internal straight, essentially parallel pores.

9. A method of step-by-step synthesis of an array of different chemical compounds at microdrop-sized loci, where each compound is covalently attached to or beneath the surface of a substrate, wherein said substrate comprises a porous material, comprising the steps of:

(a) applying through a single jet of a multiple jet reagent dispenser at least one microdrop of a first reagent in liquid form to said surface at the first locus;

(b) displacing the multiple jet reagent dispenser relative to said surface and applying through a second jet of said multiple jet reagent dispenser a second reagent in the first locus to form a mixture of reagents at the first locus wherein said substrate is chemically prepared to react with said mixture to covalently attach one or more of said reagents to said substrate at the first locus;

(c) optionally repeating steps (a) and (b) at additional microdrop sized loci of said surface where the same mixture of reagents or a different mixture of reagents are formed at each locus, wherein each reagent is dispensed from a different jet of said multiple jet reagent dispenser, and wherein said reagents in said microdrops comprise protected or unprotected nucleotides, thereby forming oligonucleotides attached at said loci;

(d) washing said substrate to remove the excess reagents;

(e) modifying said attached reagents;

(f) repeating steps (a) through (e) with the same or different reagents at various loci on the substrate until the synthesis of oligonucleotides at each of at least 20 said loci is completed;

(g) optionally removing the attached compounds at said loci from said substrate, wherein said optional removing is performed in a selective or a non selective manner, then amplifying said oligonucleotides by polymerase chain reaction amplification.

12. A method of step-by-step synthesis of an array of different chemical compounds at microdrop-sized loci, where each compound is covalently attached to or beneath the surface of a substrate, wherein said substrate comprises a porous material comprising the steps of:

(a) applying through a single jet of a multiple jet reagent dispenser at least one microdrop of a first reagent in liquid form to a loci on said surface, wherein said substrate is chemically prepared to react with said first reagent to covalently attach said reagent to said substrate;

(b) displacing said multiple jet reagent dispenser relative to said surface, or the surface with respect to said multiple jet reagent dispenser, and applying at least one microdrop containing either the first reagent or a second reagent from a different dispenser jet to a second loci on said surface wherein said substrate is chemically prepared to react with said reagent to covalently attach said reagent to said substrate;

(c) optionally repeating step (b) at least one time using either said first reagent, said second reagent, or different reagents in liquid form from different dispenser jets wherein each of said reagents covalently attaches to said substrate to form covalently attached compounds, and wherein said reagents in said microdrops comprise protected or unprotected nucleotides, thereby forming oligonucleotides attached at said loci;

(d) washing said substrate to remove unattached reagents;

(e) modifying said attached reagents;

(f) repeating steps (a) through (e) with the same or different reagents at various loci on the substrate until the synthesis of oligonucleotides at each of at least 20 said loci is completed;

(g) forming the oligonucleotide complements of said attached oligonucleotides by use of polymerase and nucleic acids, then washing said complements from said substrate with a denaturing agent.

14. A method according to claim 12 or 13 wherein said porous material comprises paper.

15. A method according to claim 12 or 13 wherein said porous material comprises a sheet having internal straight, essentially parallel pores.

20. A method according to claim 12 or 13 wherein said substrate comprises a porous membrane having straight, essentially parallel pores and said complements are removed through said pores onto a second substrate, wherein the relative locations of said complements on said second substrate correspond to the relative locations of their respective oligonucleotides on said substrate from which they were removed.

13. A method of step-by-step synthesis of an array of different chemical compounds at microdrop-sized loci, where each compound is covalently attached to or beneath the surface of a substrate, wherein said substrate comprise a porous material comprising the steps of:

(a) applying through a single jet of a multiple jet reagent dispenser at least one microdrop of a first reagent in liquid form to said surface at the first locus;

(b) displacing the multiple jet reagent dispenser relative to said surface and applying through a second jet of said multiple jet reagent dispenser a second reagent to the first locus to form a mixture of reagents at the first locus wherein said substrate is chemically prepared to react with said mixture to covalently attach one or more of said reagents to said substrate at the first locus;

(c) optionally repeating steps (a) and (b) at additional microdrop sized loci of said surface where the same mixture of reagents or a different mixture of reagents are formed at each locus, wherein reach reagent is dispensed from a different jet of said multiple jet reagent dispenser, and wherein said reagents in said microdrops comprise protected or unprotected nucleotides, thereby forming oligonucleotides attached at said loci;

(d) washing said substrate to remove the excess reagents;

(e) modifying said attached reagents;

(f) repeating steps (a) through (e) with the same or different reagents at various loci on the substrate until the synthesis of oligonucleotides at each of at least 20 said loci is completed;

(g) forming the oligonucleotide complements of said attached oligonucleotides by use of polymerase and nucleic acids, then washing said complements from said substrate with a denaturing agent.

16. A method of step-by-step synthesis of an array of different chemical compounds at microdrop-sized loci, where each compound is covalently attached to or beneath the surface of a substrate comprising the steps of:

(a) applying through a single jet of a multiple jet reagent dispenser at least one microdrop of a first reagent in liquid form to loci on said surface, wherein said substrate comprises a porous membrane having straight, essentially parallel pores, is chemically prepared to react with said first reagent to covalently attach said reagent to said substrate;

(b) displacing said multiple jet reagent dispenser relative to said surface, or the surface with respect to said multiple jet reagent dispenser, and applying at least one microdrop containing either the first reagent or a second reagent from a different dispenser jet to a second loci on said surface wherein said substrate is chemically prepared to react with said reagent to covalently attach said reagent to said substrate;

(c) optionally repeating step (b) at least one time using either said first reagent, said second reagent, or different reagents in liquid form from different dispenser jets wherein each of said reagents covalently attaches to said substrate to form covalently attached compounds, and wherein said reagents in said microdrops comprise protected or unprotected nucleotides, thereby forming oligonucleotides attached at said loci;

(d) washing said substrate to remove unattached reagents;

(e) modifying said attached reagents;

(f) repeating steps (a) through (e) with the same or different reagents at various loci on the substrate until the synthesis of oligonucleotides at each of at least 20 said loci is completed;

(g) hybridizing oligonucleotide complements to said attached oligonucleotides, then washing said complements through said pores onto a second substrate, wherein the relative locations of said complements on said second substrate correspond to the relative locations of their respective oligonucleotides on said substrate from which they were removed.

18. A method according to claim 16 or 17 wherein said porous membrane comprises paper.

19. A method according to claim 16 or 17 wherein said porous material comprises a sheet having internal straight, essentially parallel pores.

26. A substrate prepared according to the method of claim 16 or 17.

17. A method of step-by-step synthesis of an array of different chemical compounds at microdrop-sized loci, where each compound is covalently attached to or beneath the surface of a substrate comprising the steps of:

(a) applying through a single jet of a multiple jet reagent dispenser at least one microdrop of a first reagent in liquid form to said surface of said substrate at the first locus, and wherein said substrate comprises a porous membrane having straight, essentially parallel pores;

(b) displacing the multiple jet reagent dispenser relative to said surface and applying through a second jet of said multiple jet reagent dispenser a second reagent to the first locus to form a mixture of reagents at the first locus wherein said substrate is chemically prepared to react with said mixture to covalently attach one or more of said reagents to said substrate at the first locus;

(c) optionally repeating steps (a) and (b) at additional microdrop sized loci of said surface where the same mixture of reagents or a different mixture of reagents are formed at each locus, wherein each reagent is dispensed from a different jet of said multiple jet reagent dispenser, and wherein said reagents in said microdrops comprise protected or unprotected nucleotides, thereby forming oligonucleotides attached at said loci;

(d) washing said substrate to remove the excess reagents;

(e) modifying said attached reagents;

(f) repeating steps (a) through (e) with the same or different reagents at various loci on the substrate until the synthesis of oligonucleotides at each of at least 20 said loci is completed;

(g) hybridizing oligonucleotide complements to said attached oligonucleotides, then washing said complements through said pores onto a second substrate, wherein the relative locations of said complements on said second substrate correspond to the relative locations of their respective oligonucleotides on said substrate from which they were removed.

21. A method of step-by-step synthesis of an array of different chemical compounds at microdrop-sized loci, where each compound is covalently attached to or beneath the surface of an undifferentiated substrate comprising the steps of:

(a) applying through a single jet of a multiple jet reagent dispenser at least one microdrop of a first reagent in liquid form to a loci on said surface, wherein said undifferentiated substrate is porous material comprising a sheet having internal straight, essentially parallel pores, and is chemically prepared to react with said first reagent to covalently attach said reagent to said undifferentiated substrate;

(b) displacing said multiple jet reagent dispenser relative to said surface, or the surface with respect to said multiple jet reagent dispenser, and applying at least one microdrop containing either the first reagent or a second reagent from a different dispenser jet to a second loci on said surface wherein said substrate is chemically prepared to react with said reagent to covalently attach said reagent to said substrate;

(c) optionally repeating step (b) at least one time using either said first reagent, said second reagent, or different reagents in liquid form from different dispenser jets wherein each of said reagents covalently attaches to said substrate to form covalently attached compounds;

(d) washing said substrate to remove unattached reagents;

(e) modifying said attached reagents; and

(f) repeating steps (a) through (e) with the same or different reagents at various loci on the substrate until the synthesis of different chemical compounds at each of at least 20 said loci is completed, wherein said compounds attached at said loci are cleavable from said substrate by exposure to laser or electron beams.

23. A method according to claim 21 or 22 wherein said undifferentiated substrate comprises a solid, non-porous material.

24. A method according to claim 21 or 22 wherein said substrate comprises a porous material.

25. A method according to claim 24 wherein said porous material comprises paper.

22. A method of step-by-step synthesis of an array of different chemical compounds at microdrop-sized loci, where each compound is covalently attached to or beneath the surface of an undifferentiated substrate comprising the steps of:

(a) applying through a single jet of a multiple jet reagent dispenser at least one microdrop of a first reagent in liquid form to said surface at the first locus of said undifferentiated substrate, wherein said undifferentiated substrate is a porous material comprising a sheet having internal straight, essentially parallel pores;

(b) displacing the multiple jet reagent dispenser relative to said surface and applying through a second jet of said multiple jet reagent dispenser a second reagent to the first locus to form a mixture of reagents at the first locus wherein said substrate is chemically prepared to react with said mixture to covalently attach one or more of said reagents to said substrate at the first locus;

(c) optionally repeating steps (a) and (b) at additional microdrop sized loci of said surface where the same mixture of reagents or a different mixture of reagents are formed at each locus, wherein each reagent is dispensed from a different jet of said multiple jet reagent dispenser;

(d) washing said substrate to remove the excess reagents;

(e) modifying said attached reagents; and

(f) repeating steps (a) through (e) with the same or different reagents at various loci on the substrate until the synthesis of different chemical compounds at each of at least 20 said loci to completed, wherein said compounds attached at said loci are cleavable from said substrate by exposure to laser or electron beams.

27. A method of step-by-step synthesis of an array of different chemical compounds at microdrop-sized loci, where each compound is covalently attached to or beneath the surface of an undifferentiated substrate comprising the steps of:

(a) applying through a single jet of a multiple jet reagent dispenser, consisting of multiple piezoelectric jet heads, at least one microdrop of a first reagent in liquid form to a loci on said surface, wherein said undifferentiated substrate is a porous material comprising a sheet having internal straight, essentially parallel pores, and is chemically prepared to react with said first reagent to covalently attach said reagent to said undifferentiated substrate;

(b) displacing said multiple jet reagent dispenser relative to said surface, or the surface with respect to said multiple jet reagent dispenser, and applying at least one microdrop containing either the first reagent or a second reagent from a different dispenser jet to a second loci on said surface wherein said substrate is chemically prepared to react with said reagent to covalently attach said reagent to said substrate;

(c) optionally repeating steps (b) at least one time using either said first reagent, said second reagent, or different reagents in liquid form from different dispenser jets wherein each of said reagents covalently attaches to said substrate to form covalently attached compounds;

(d) washing said substrate to remove unattached reagents;

(e) modifying said attached reagents;

(f) repeating steps (a) through (e) with the same or different reagents at various loci on the substrate until the synthesis of different chemical compounds at each of at least 20 said loci is completed, and

(g) optionally removing the attached compounds at said loci from said substrate, wherein said optional removing is performed in a selective or a non-selective manner.

29. A method according to claim 27 or 28 wherein said substrate comprises a solid, non-porous material.

30. A method according to claim 27 or 28 wherein said substrate comprises a porous material.

31. A method according to claim 30 wherein said porous material comprises paper.

28. A method of step-by-step synthesis of an array of different chemical compounds at microdrop-sized loci, where each compound is covalently attached to or beneath the surface of an undifferentiated substrate comprising the steps of:

(a) applying through a single jet of a multiple jet reagent dispenser, consisting of multiple piezoelectric jet heads, at least one microdrop of a first reagent in liquid form to said surface at the first locus of said undifferentiated substrate, wherein said undifferentiated substrate is a porous material comprising a sheet having internal straight, essentially parallel pores;

(b) displacing the multiple jet reagent dispenser relative to said surface and applying through a second jet of said multiple jet reagent dispenser a second reagent to the first locus to form a mixture of reagents at the first locus wherein said substrate is chemically prepared to react with said mixture to covalently attach one or more of said reagents to said substrate at the first locus;

(c) optionally repeating steps (a) and (b) at additional microdrop sized loci of said surface where the same mixture of reagents or a different mixture of reagents are formed at each locus, wherein each reagent is dispensed from a different jet of said multiple jet reagent dispenser;

(d) washing said substrate to remove the excess reagents;

(e) modifying said attached reagents;

(f) repeating steps (a) through (e) with the same or different reagents at various loci on the substrate until the synthesis of different chemical compounds at each of at least 20 loci is completed; and

(g) optionally removing the attached compounds at said loci from said substrate, wherein said optional removing is performed in a selective or a non-selective manner.