Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Organic polymerization
Reexamination Certificate
1998-01-16
2002-07-16
Wilson, James O. (Department: 1623)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Organic polymerization
C422S105000, C422S111000, C422S129100, C422S131000, C422S134000, C422S136000, C422S149000
Reexamination Certificate
active
06419883
ABSTRACT:
1. FIELD OF THE INVENTION
The present invention relates to chemical synthesis, particularly synthesis of biopolymers such as oligonucleotides and peptides, using solvent microdroplets as a means for reagent delivery.
2. BACKGROUND OF THE INVENTION
Genetic information generated by the Human Genome Project is allowing scientists, physicians, and others to conduct diagnostic and experimental procedures on an unprecedented scale in terms of speed, efficiency, and number of screenings performed within one procedure. In order to make full use of this new information, there is an urgent need for the ability to screen a large number of chemical compounds, particularly oligonucleotide probes, against samples of DNA or RNA from normal or diseased cells and tissue. One important tool for such analyses is nucleic acid hybridization, which relies on the difference in interaction energies between complementary and mismatched nucleic acid strands (see U.S. Pat. No. 5,552,270 to Khrapko et al.). Using this tool, it is possible to determine whether two short pieces of nucleic acid are exactly complementary. Longer nucleic acids can also be compared for similarity.
Nucleic acid hybridization is often used for screening cloned libraries to identify similar, and thus presumably related, clones. This procedure typically involves using (a) natural nucleic acid targets which are usually bound to a membrane, and (b) a natural or synthetic nucleic acid probe which is washed over many targets at once. With the appropriate mechanics, membranes can be constructed with targets at a density of generally between one and ten targets per mm
2
. Hybridization detection is carried out by labeling the probe, for example either radioactively or with chemiluminescent reagents, and then recording the probe's emissions onto film.
Alternative approaches to nucleic acid hybridization have involved oligonucleotide probes that are synthesized on a solid support or a substrate, and then hybridized to a single natural target. Solid phase synthesis techniques for obtaining peptides (K. S. Lam et al.,
Nature
354:82 (1991) and Geysen et al.,
J. Immunol. Methods
102:259 (1987)) and oligonucleotides (J. Weiler et al.,
Anal. Biochem.
243:218 (1996) and U. Maskos et al.,
Nucleic Acids Res.
20(7):1679 (1992); T. Atkinson et al.,
Solid
-
Phase Synthesis of Oligodeoxyribonucleotides by the Phosphitetriester Method, in Oligonucleotide Synthesis
35 (M. J. Gait ed., 1984) have been disclosed. While such approaches have the potential for large-scale assembly of oligonucleotide arrays, the cost of making such a variety of arrays is prohibitive.
Recently, there have been reports of using microdrop dispensers to generate oligomers and polymers arranged, on a substrate, in arrays of microdroplets:
1. T. Brennan, Human Genome Program, U.S. Department of Energy, Contractor-Grantee Workshop III, Feb. 7-10, 1993, Santa Fe, N. Mex.,
Methods to Generate Large Arrays of Oligonucleotides
92 (1993), discloses that arrays of oligonucleotides were sought to be synthesized in parallel chemical reactions on glass plates, using arrays of piezoelectric pumps, similar to an inkjet printer, as a means for delivering reagents. In such a scheme, each array element is separated by its neighbor by a perfluoroalkane tension barrier which is not wet by the acetonitrile reaction solvent.
2. U.S. Pat. No. 5,449,754 to Nishioka discloses that peptide arrays can be obtained using an inkjet print head to deposit a dimethylformamide solution of N-protected activated amino acids, in the form of microdroplets, onto an aminosilylated glass slide which is subsequently washed with a trifluoroacetic acid solution to remove the N-protecting groups from the anchored amino acids. The process is repeated until amino acids having the desired sequence are obtained.
3. U.S. Pat. No. 5,474,796 to Brennan describes a piezoelectric impulse jet pump apparatus for synthesizing arrays of oligomers or polymers having subunits connected by ester or amide bonds. According to that scheme, a glass plate is coated with a fluoropolymer which is then selectively removed, leaving glass regions, in spots upon which oligomer or polymer synthesis would take place. The glass regions are epoxidized and subsequently hydrolyzed to afford a hydroxyalkyl group that would react with an activated chemical species. Where the oligomers sought to be synthesized are oligonucleotides, microdroplets of acetonitrile or diethyleneglycol dimethyl ether solutions of 5′-protected nucleotide monomers that are activated at their 3′-positions would be dispensed via a piezoelectric jet head, and would impinge upon the hydroxyalkyl group, forming a covalent bond therewith. After removing the 5′-protecting groups by flooding the surface of the plate with a deprotecting reagent, the process is repeated until the desired oligonucleotides are obtained.
4. International Publication No. WO 95/25116 by Baldeschwieler et al. discloses a method for chemical synthesis at different sites on a substrate using an inkjet printing device to deliver reagents to specific sites of the substrate. In that instance, the inkjet printing device would deposit, in sequence, (a) a protected molecule onto the substrate, (b) a deprotecting reagent onto the protected molecule so as to expose a reactive site, and (c) a second protected molecule at the site of the now-deprotected molecule, so as to form a growing chain of molecules. The entire process is repeated as necessary. According to this publication by Baldeschwieler et al., useful reaction solvents are dibromomethane, nitromethane, acetonitrile and dimethylformamide.
5. U.S. Pat. No. 5,658,802 to Hayes et al. discloses a dispensing apparatus that is allegedly capable of providing droplets having a volume of 10 pL to 100 pL, and purportedly useful for synthesizing arrays of diagnostic probes. According to that reference, the dispensing apparatus is capable of dispensing “liquids” that may contain DNA molecules, peptides, antibodies, antigens, enzymes or entire cells; however, no specific examples of such “liquids” are disclosed.
There exists a need for a method of efficiently synthesizing chemical compounds on a large scale that can be automated. Prior art suggestions for achieving such involve various drawbacks.
The present inventor has realized the nature of these drawbacks, which is overcome by the present invention. In particular, the dispensation of certain organic solvents from an inkjet printing device for use in chemical synthesis has several drawbacks. First, many organic solvents, such as alcohols or amines, bear functional groups that are capable of reacting with those chemical compounds sought to be dispensed from the inkjet device. Second, solvents having boiling points of less than 150° C. are relatively volatile, and can evaporate from a substrate before the reactant(s) dissolved therein have completely reacted with any species bound to the substrate. Third, such volatile solvents can begin to evaporate at the site of the inkjet print head, causing reactants dissolved in the solvents to precipitate and clog the inkjet nozzle. Fourth, solvents that have surface tension values that are lower than 30 dynes/cm at room temperature have a relatively high affinity for the face of the inkjet nozzle, and tend to give rise to unstable and non-uniformly sized droplets. Fifth, solvents that have viscosity values that are lower than 1 centipoise at room temperature tend to form non-uniformly sized droplets due to their response to residual oscillations in the solvent. Sixth, many organic solvents, particularly acetonitrile, have the highly undesirable characteristic of being capable of dissolving adhesives and plastics used in inkjet print heads. Thus, prior to the present invention the organic solvents used for synthesizing oligonucleotides were ineffective in automated systems employing plastic components such as ink jet print heads.
Thus, there exists a need for a class of organic solvents, useful for chemical synthesis, that is relatively inert, and that
Campbell & Flores LLP
University of Washington
Wilson James O.
LandOfFree
Chemical synthesis using solvent microdroplets does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Chemical synthesis using solvent microdroplets, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Chemical synthesis using solvent microdroplets will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2833386