Device for carrying out chemical reactions

The invention relates to an apparatus for the conduct of chemical reactions, comprising:    The invention is distinguished on the one hand by a device to apply a predetermined force to the sliders and on the other hand by a valve assembly by means of which chemicals may be supplied to the chemical slider in premixed form.

The invention relates to an apparatus for the conduct of chemical reactions. In particular the invention relates to an apparatus for the conduct of chemical syntheses, preferably for the synthesis of oligonucleotides.

Such apparatuses are known for example from EP 0 146 206 B1 and EP 0 181 491 B1. These apparatuses each have several reaction discs arranged above one another in stacks and in each of which are arranged three or four continuous thin bores serving as ducts and a bore with at least partially greater cross-section serving as reaction vessel. The reaction discs have a central bore through which passes a pin serving as connecting element. The ends of each pin are provided with a thread, on which is screwed a nut, to hold the reaction discs together with considerable force.

The reaction discs may be rotated around the pins, which involves loosening the screw connection. By rotating the reaction discs around the pins, the ducts are brought into alignment with one of the reaction chambers, in order to supply a specific reagent to the reaction vessel.

JP 62 298599 A discloses an apparatus similar in design to the apparatus according to EP 0 164 206 B1, but with only a single reaction vessel in each disc.

Such apparatuses have not proved successful in practice, since the number of reactions which may be carried out simultaneously is limited and, for each change in the combination of reagents to be supplied to a particular reaction chamber, the screw connection must be released and the reaction discs rearranged by hand.

Described in DE 38 13 671 A1 is an apparatus for the conduct of chemical reaction sequences which has a stack of reaction plates arranged on top of one another and optionally movable relative to one another in steps, and with passages arranged at the step spacing, one of which in each case forms a reaction chamber. A plate adjustment device provides for the optional shifting of a particular plate relative to the rest of the plate stack. A lever mechanism is provided to apply pressure to the plates after movement, so as to ensure a perfect seal of the passages formed in the plates.

Known from EP 629 144 B1 is an apparatus for the conduct of chemical reactions proceeding simultaneously or consecutively, in which chemical reactions may proceed simultaneously in a multiplicity of reaction chambers, as e.g. in the synthesis of oligonucleotides. Provided for this purpose instead of discs are rods, arranged on top of one another and automatically movable relative to one another. A single rod contains a large number of reaction chambers. Below and above each of the rods with reaction chambers is a rod with a single through hole, by means of which in each case a particular reaction chamber may be connected on one side to a vessel containing a reagent, and on the other side to a suction pump to draw the reagent into the reaction chamber. In particular it is possible to perform a large number of such suction processes at short intervals of time, with scope for selecting a different reagent and a different reaction chamber in each case. By this means any desired combinations of reagents may be combined in the reaction chambers and brought to chemical reaction in rapid sequence.

A further advantage of this known apparatus is that both the dead volumes required for control of chemicals and also the reaction chambers can be kept small, thereby minimising consumption of reagents which—in particular for oligonucleotide synthesis—are very expensive. In further known apparatuses (e.g. DE 35 25 678 A1) valves are used to control the flow of chemicals. Such valves have a large dead volume, resulting in a low chemical efficiency.

In the apparatus known from EP 0 629 144 B1, the rods are pressed together with high pressure, so that their contact faces fit tightly together and no reagents creep between the rods. However, when the rods are moved against one another, the high pressure results in considerable wear. It is also difficult to manufacture elongated rods of this kind with the necessary precision and strength. There is always the danger of such rods becoming distorted during hardening. The maximum number of reaction chambers is limited by the maximum length of the rods which can be made at a reasonable technical and economic cost.

WO 98/57181 describes an apparatus with several reaction vessels arranged in a carousel. The carousel is driven via a belt by means of a stepping motor, so that it can be rotated around a central, vertical axis. The individual reaction vessels are arranged concentrically to this axis. On the top of the carousel is an injection plate and on the bottom an evacuation plate. These two plates are static and are provided with passages so that a fluid may be conveyed from the injection plate through a reaction vessel and through an opening in the evacuation plate. A clamping mechanism is provided in such a way that the position of the plates may be controlled in a suitable manner.

The invention is based on the problem of developing an apparatus for the conduct of chemical reactions of the type described above so that, despite a simple and compact design, a high throughput is ensured by a large number of reaction chambers.

The problem is solved by an apparatus with the characteristics of claim1and by an apparatus with the characteristics of claim9respectively. Advantageous developments are set out in the subsidiary claims.

The apparatus according to the invention for the conduct of chemical reactions comprises:a reaction slider in which are formed a multiplicity of through holes serving as reaction chambers,a selector slider located on a side of the reaction slider at which the reaction chambers emerge, and having a continuous control orifice, wherein the selector slider is movable relative to the reaction slider,a chemical slider, located on the opposite side of the reaction slider to the selector slider, wherein feed holes for the supply of chemicals emerge on the surface of the chemical slider facing the selector slider, and the reaction chambers of the reaction slider and the feed holes of the chemical slider are arranged along an orbit, and the reaction slider and the selector slider may be so moved by rotation around a common axis of rotation which passes through the centre point of the orbit that one of the feed holes, one of the reaction chambers and the control orifice may be brought into alignment, so that a through connection to supply the reaction chamber with a predetermined reagent may be made, and a device is provided to apply a force to the sliders in order to seal their contact faces, this device being so designed that the force acts in the area of the axis of rotation.

This circular arrangement of the reaction chambers on the reaction slider allows the reaction slider to have a very compact design with a multiplicity of reaction chambers.

This circular arrangement of the reaction chambers, combined with the centrally-acting pressure-loading device for pressing the sliders together, generates a pressure distribution which is symmetrical around the axis of rotation, so that even with a multiplicity of reaction chambers pressure is distributed evenly on the areas of the individual reaction chambers. By this means it is ensured that, despite there being a multiplicity of reaction chambers, they are reliably sealed. The invention makes it possible to provide many reaction chambers, thus obtaining a high throughput, while the sealing of the many reaction chambers is simultaneously ensured.

With this pressure-loading device the sliders can be pressed together in a defined position with a predetermined force, e.g. 100 N, while the force is reduced or released to rotate the sliders, so that wear is minimised and the seal at the contact faces of the sliders is maintained over a long period of time.

Due to the circular form of the reaction sliders, the sliders may be plate-shaped and may be made in particular in the form of an annular disc, thereby considerably reducing the cost of production in comparison with the rods known from EP 0 629 144 B1. This is based on the fact, amongst other things, that plates may be designed with flat surfaces much more easily than rods, which also often become distorted during hardening. This circular arrangement of the reaction chambers thus allows simpler manufacture of flat and therefore leakproof contact faces.

According to a further preferred embodiment, there is provided a drive unit with a cylindrical stationary drive housing and two concentric hollow shafts arranged one inside the other, on which the reaction slider and the selector slider may be placed so as to be non-rotatable. This provision of the drive unit separate from the sliders permits simple and rapid replacement of the sliders, which may be non-rotatably connected to the drive unit, preferably by means of a plug-in connection. By this means it is possible e.g. to change the number of reaction chambers by exchanging the reaction slider, in order to adapt to particular requirements.

The solution according to claim8provides an apparatus for the conduct of chemical reactions with:a reaction slider in which are formed a multiplicity of through holes serving as reaction chambers,a selector slider located on a side of the reaction slider at which the reaction chambers emerge, and having a continuous control orifice, wherein the selector slider is movable relative to the reaction slider,a chemical slider, located on the opposite side of the reaction slider to the selector slider, wherein feed holes for the supply of chemicals emerge on the surface of the chemical slider facing the selector slider, and the reaction chambers of the reaction slider and the feed holes of the chemical slider are arranged along an orbit, and the reaction slider and the selector slider may be so moved by rotation around a common axis of rotation which passes through the centre point of the orbit that one of the feed holes, one of the reaction chambers and the control orifice may be a lower area 5 of smaller internal diameter. If the apparatus according to the invention is meant to be used for the synthesis of oligonucleotides then frit, in itself known, is used to hold the reagents.

The reaction chambers3may also be designed to hold cartridges, which are described in German registered design application DE 299 21 606.3. Such cartridges facilitate the sealing of the reaction chambers.

In addition to the reaction chambers3, the orbit also has two through holes with a continuously narrow internal diameter, which are used as flushing passages6. The two flushing passages6are diametrically opposite on the orbit, and divide the reaction chambers3into two sections of twelve reaction chambers3each. The reaction slider2is provided with a central opening7. Adjacent to the central opening7are three continuous drive holes8arranged at the same angular distance around the centre point of the reaction slider2.

In the apparatus according to the invention the reaction slider2is mounted horizontally, with a selector slider9provided adjacent to its top side. In the present embodiment the selector slider9is comprised of a steel plate with a central opening11which is circular viewed from above. Adjacent to the central opening11, the selector slider9has three drive holes12arranged at the same angular distance. The selector slider9has a larger diameter than the reaction slider2. Provided in the selector slider9is a continuous vertical control orifice15. The control orifice15of the selector slider9is positioned from the centre point of the selector slider9at a distance equal to the radius r of the orbit on which the reaction chambers3of the reaction slider2are arranged so that, when the selector slider9is rotated, the control orifice15describes the same orbit as the reaction chambers3.

By this means, by rotating the selector slider9relative to the reaction slider2around the common vertical central axis16, the control orifice15may be brought into alignment with any one of the reaction chambers3or with one of the flushing passages6, resulting in each case in a continuous passage through the selector slider9and the reaction slider2.

The selector slider9and the reaction slider2are mounted on a chemical slider17. The chemical slider17is a steel ring with for instance a rectangular, for example square, cross-section. The chemical slider-17is arranged concentrically to the common vertical axis16and has a multiplicity of through holes18, arranged along an orbit with radius r around the common axis16. The through holes18are preferably spaced at an equal distance from one another around the orbit, with the distance between two adjacent through holes18preferably differing from the distance between two adjacent reaction chambers3of the reaction slider2, so that in each case only a single through hole18can be in communication with a single reaction chamber3.

In an alternative embodiment, the angular distances between two adjacent through holes18correspond to the angular distances between two adjacent reaction chambers3. With this embodiment, in the pauses between two chemical supply processes the reaction slider2is moved by an intermediate step relative to the chemical slider17, corresponding e.g. to half the angular distance between two adjacent reaction chambers3, so that none of the reaction chambers3is aligned with any of the through holes18, and the reaction chambers3do not overlap any of the through holes18. By this means, any flow of chemicals into the reaction chambers3is reliably prevented.

The through holes18of the chemical slider17are bent towards its outer circumferential surface53, where they emerge in the form of connection orifices21. Connected to the connection orifices21are chemical feed lines19e.g. in the form of tubing, each leading to a valve assembly54, via which two or more different chemicals may be supplied to the chemical feed line.

In the embodiment depicted inFIG. 1, some of the chemical feed lines19divide into two branch lines19a,19b, each having a control valve55and leading to a chemical container20containing a predetermined reagent. The through holes18of the chemical slider17connected to a branching chemical feed line19may thus be supplied with a predetermined reagent or with a predetermined mixture of two reagents. The through holes18thus function as chemical feed orifices for feeding chemicals to the reaction chambers3of the reaction slider2.

Each of the unbranched chemical feed lines19leads to a single chemical container20. Expediently located in these chemical feed lines are further control valves55, which are able to prevent an unintended flow of chemicals from one of the chemical containers20to a reaction chamber3.

In the apparatus according to the invention the chemical slider17is stationary and, for rotation of the selector slider9and the reaction slider2, each of the latter is provided with a drive unit (not shown inFIG. 1), so that the selector slider9may be rotated through at least one full revolution (360°) around the common axis16independently of the reaction slider2. The control orifice15of the selector slider9is connected via a further line (not shown) to a metering pump.

The basic mode of operation of the slider assembly shown inFIG. 1, for the conduct of chemical reactions, will be explained in detail below.

The individual chemical containers20contain various reagents so that two reagents may be fed to the relevant through holes18of the chemical slider17via the valve assemblies54. By locating one of the reaction chambers3over a specific through hole18of the chemical slider17, and by simultaneous placing of the control orifice15of the selector slider9over this reaction chamber3, one or more reagents may be fed to the reaction chamber3from the predetermined through hole18by suction using a metering pump (not shown). In the case of the valve assemblies of the present embodiment, comprised of two valves55, either a single valve can be opened so that only a single reagent is supplied, or else both valves may be opened simultaneously or alternately in quick succession so that a mixture of two reagents is supplied.

If an oligonucleotide synthesis is to be conducted then it is expedient to supply the reagents containing the basic structural elements (phosphite amides) mixed with an activator (e.g. tetracol in acetonitrile) since, by premixing the two reagents immediately before feeding them to a reaction chamber, a significantly better reaction is obtained in a shorter time than if the two reagents were supplied intermittently, one after the other.

When the desired amount of a reagent or a mixture of reagents has reached the reaction chamber3, then the reaction slider2and/or the selector slider9are rotated, thereby breaking the connection from a chemical container20to the metering pump, so that no further flow of chemicals is possible. This reaction chamber3may be removed from the through hole18of the chemical slider17by a short turning movement, so that the reaction chamber3is also closed at its lower end. This chemical flow may also be stopped by closing the relevant valves control valve55.

The process of drawing a specific reagent or mixture of reagents into a specific reaction chamber3may be repeated as desired. At the same time the reagents and/or the reaction chambers3may be changed in any desired sequence so that a specific amount of a predetermined reagent is fed to each reaction chamber at a predetermined point in time. Since the different rotary positions of the sliders may be set in a few fractions of a second, the individual reaction chambers3may be supplied virtually simultaneously with the same or a different sequence of reagents. Specific chemical reactions may thus be generated in the individual reaction chambers3in a targeted manner.

Preferably the sliders, in particular the reaction slider2, are conditioned to a temperature suitable for the chemical reactions concerned.

FIG. 2shows schematically, in a sectioned perspective view, a further embodiment of a chemical slider17. This chemical slider17is comprised of an annular body with an outer circumferential surface53, bevelled at the top and bottom edges to give surfaces53a,53brunning at an angle to the circumferential surface53.

Two types of through holes18a,18bare provided. The overwhelming majority of through holes18aemerge at the upper surface of the chemical slider17and are bent at right-angles to the circumferential surface53. Provided at this exit point of the through hole18ais a multiway valve56, which is connected to each of the upper and lower branch lines57,58formed in the chemical slider17. Each of the two branch lines57,58leads from the circumferential surface53to a connection recess59formed on the upper or lower bevel53a,53b. These connection recesses59may each accommodate a connection element60connected to a tube (not shown). Each of the tubes is connected to a chemical container20and represents a part of the branch lines57,58. In the present embodiment the multiway valves56are designed as 2-way valves, connecting one of the through holes18to either the upper or lower branch line57,58. These 2-way valves56have only two states: in one state the upper branch line, and in the other state the lower branch line, is connected to the through hole18. Such valves have only an extremely low dead volume, so that the losses of chemicals generated by them are very small.

The second type of through hole18bleads from the upper surface of the chemical slider17to a single connection recess59, located on the lower bevel53b, and in which may be accommodated a connection element60connected to a tube (not shown) leading to a chemical container.

In the synthesis of oligonucleotides, the following reaction processes are conducted consecutively to add one base in each case. Firstly the 5′ protective group is separated from an existing oligonucleotide or an initiating reagent. For this purpose a separating reagent (e.g. trichloroacetic acid) is fed to the reaction chamber.

After the separation process a base is added, by feeding the base reagent (phosphite amide) into the reaction chamber, together with an activator (tetracol in acetonitrile).

The separation process is followed by a capping process in which, by means of two capping reagents (cap-A: acetic anhydride dissolved in tetrahydrofuran; cap-B: n-methyl-timidazole dissolved in tetrahydrofuran and a trace of pyridine or colidine) the 5′-ends—activated but not provided with a base—are blocked from any further addition of bases. This prevents the formation of oligonucleotides with undesired base combinations.

The next stage is the oxidation of trivalent phosphorus into pentavalent phosphorus by the addition of iodine dissolved in acetonitrile.

These reaction processes are repeated to add one base at a time. Between each of the individual reaction processes a rinsing reagent (e.g. acetonitrile) is passed through the reaction chambers to remove excess reagents.

During both the addition process and also the capping process a mixture of two reagents, which can not be stocked as a mixture, is fed to the reaction chamber. Using the apparatus according to the invention, these mixtures are mixed at the chemical slider17. The mixing is effected by rapid alternate connection of the branch lines57,58to the through hole18, by means of which the two reagents are intermittently fed to the reaction chamber and mixed. After such a mixture has been fed it is expedient to purge the section of line leading from the valve assembly to the reaction chamber and the reaction chamber itself. The cheapest of the two reagents in the mixture is used for purging.

The reagents (separating reagent, oxidation reagent, rinsing reagent) supplied for the reaction processes in unmixed form are fed to the reaction chamber from the respective chemical container via an unbranched chemical feed line and one of the through holes18b, without the interposition of a valve assembly with a multiway valve.

In the case of this embodiment it is expedient to provide a control valve (not shown) in both the branched and also in the unbranched chemical feed lines, so as to prevent any undesired flow of chemicals.

The chemical slider17according to the invention has at least five through holes18a(for four bases and the respective activator and the two capping reagents) connected to a valve assembly and at least three unbranched through holes18b(for the separating reagent, rinsing reagent, oxidation reagent).

FIG. 3shows schematically in simplified form a further embodiment of a chemical slider17. This chemical slider has only five through holes18, each connected to a valve assembly via a chemical feed line19. One of the five valve assemblies is a 7-way valve assembly54with seven valves55, each controlling the flow of chemicals from a chemical container20. A further valve assembly54is a 2-way valve assembly54with two valves55, each controlling the flow of chemicals from a chemical container. The remaining three valve assemblies are 1-way valve assemblies, each comprised of a single valve55.

Connected to the 7-way valve assembly are chemical containers20with a first purging agent S1(e.g. argon), a second purging agent S2(e.g. acetonitrile), an activator AK and the four base reagents A, C, G and T.

Connected to the 2-way valve assembly are chemical containers20with the two capping reagents CA and CB. Connected to the 1-way valve assemblies are chemical containers with a separating reagent AB or an oxidation reagent O or a rinsing reagent W. The chemical containers20with the purging agents S1and S2are located at the end of the chemical feed line19furthest from the through holes18, so that they purge the whole of the chemical feed line and are thereby able to remove all residues of the other chemicals.

A disadvantage of this embodiment as compared with the embodiment shown inFIG. 2is that the line section connecting the individual valves55and the line section leading to the through holes18form a dead volume during the changeover from one reagent to another reagent. Unused chemicals have to be purged from this dead volume, without ever being used. This disadvantage may be limited by short line routing, and is taken into consideration for applications in which specific mixtures of base reagents are fed to the reaction chambers in order to produce in a reaction chamber predetermined amounts of e.g. oligonucleotides differing at a single point. There is an increasing demand for such oligonucleotides which differ only slightly at one or a few points.

A further advantage of this embodiment is that the chemical slider17has only a few through holes18. For these it is easy to select an angular distance which differs from the angular distance of two adjacent reaction chambers3in such a way that in each case only a single through hole18is aligned with one of the reaction chambers3, while the other through holes are neither aligned with nor overlap other reaction chambers. If the reaction slider is rotated a little, all communicating connections between the through holes18and the reaction chambers3are broken, and any undesired flow of chemicals is reliably prevented.

If further bases or other chemicals are be added, then further valve assemblies with two to seven or more valves may be provided.

The mechanical set-up of an apparatus according to the invention for the conduct of chemical reactions will be explained in detail below with the aid ofFIG. 4.

This apparatus1has a unit comprised of a reaction slider2, a selector slider9and a chemical slider17, with a design substantially the same as that of the unit depicted inFIG. 1.

This unit comprised of the sliders2,9and17is mounted on a drive unit22. The drive unit22has an approximately cylindrical stationary drive housing23and two concentric hollow shafts24,25arranged one inside the other. The hollow shaft24adjacent to the drive housing23is pivotably mounted relative to the drive housing23by means of two bearings26. Fitted between the two bearings26is a spacer bush27, in order to keep the bearings26a predetermined distance apart. The innermost hollow shaft25is in turn pivotably mounted relative to the hollow shaft24by means of two further bearings28.

Fitted to the upper end face of the drive housing23are pins29which extend vertically upwards and engage in corresponding blind holes30of the chemical slider17.

The upper end face of the innermost hollow shaft25is provided with drive pins31which project vertically upwards and engage in the drive holes12(FIG. 1) of the selector slider9. In similar fashion, drive pins32engaging in the drive holes8of the reaction slider2are provided on the upper end face of the hollow shaft24which is adjacent to the drive housing23.

The chemical slider17, the selector slider9and the reaction slider2are thus connected non-rotatably, by means of a releasable plug-in connection, with the drive housing23and the two hollow shafts24,25respectively. Provided at the bottom end of the two hollow shafts24,25and extending radially outwards from them are gear rims33,34, on which a stepping motor (not shown) can act, in each case connected via a toothed belt. In its lower section the drive housing23is non-rotatably connected to a baseplate35, while the entire drive unit22extends through an opening36formed in the baseplate35.

On the selector slider9lies a pressure plate37, non-rotatably connected to the selector slider9by means of a screw connection38. The pressure plate37is provided with a central opening37a, through which passes the common, vertical axis16of the sliders2,9,17. In addition the innermost hollow shaft25is mounted concentrically to the axis16, thus forming a passage from the pressure plate37to the bottom end section of the drive unit22. Located in this passage is a connecting rod39, which extends upwards above the pressure plate37and downwards a little below the drive unit22. At its upper end the connecting rod39is connected to a pressure piston40which lies on top of the pressure plate37, while a bearing41is inserted between the pressure piston40and the pressure plate37, so that the pressure plate37may be rotated relative to the pressure piston40. Pivoted at the lower end of the connecting rod39is a rocker arm42, which extends roughly parallel to the baseplate35and is rotatably attached to a tilting hinge43at its longitudinal centre. The tilting hinge43is mounted on a web44extending downwards from the baseplate35.

At the end of the tilting hinge43which is furthest from the connecting rod39, a vertically upright armature bar46is pivotably attached by means of an intermediate linkage45. The armature bar46runs through a further opening47in the baseplate35, and through an electromagnet mounted in a magnet housing48. The top end of the armature bar46projects from the magnet housing48. Provided in the magnet housing48is a cylinder-barrel-shaped armature through which the armature bar46passes. The armature is firmly connected to the armature bar46. A pressure-loaded spiral spring50rests on the top of the magnet housing48and is connected to the bottom end of the armature bar46.

In the de-energised state of the electromagnet48, the armature is shifted upwards, so that the armature bar46is pressed upwards by the action of the spiral spring50. The force exerted by the armature bar46on the rocker arm42is converted by the latter into a downwards-acting tensile force on the connecting rod39, which in turn presses the pressure piston40downwards against the pressure plate37. The sliders2,9and17are thus pressed together between the drive housing23and the pressure plate37with a predetermined force, which may be e.g. 100 Newtons.

If the electromagnet48energised, then the armature is pulled into the electromagnet, causing the armature bar46to drop and the connecting rod39to lift, whereby the pressure on the sliders2,9,17is reduced or even lifted completely.

In the apparatus according to the invention, during rotation of the selector slider9and/or the reaction slider2, the pressure acting on the contact faces between the sliders may therefore be temporarily reduced or completely lifted, so that the wear from rotation of the sliders is significantly less than in the case of conventional automatically operating apparatus. In addition, the application of pressure ensures the necessary sealing during suction of reagents.

For further avoidance of slider wear, the sliders may be provided with a PFD—or a ceramic coating. Instead of steel sliders, sliders of plastic, ceramic or glass materials, in particular material such as Teflon with low sliding resistance and good resistance to chemicals, are possible.

The invention has been explained above with the aid of an embodiment with 24 reaction chambers. 48 or 96 reaction chambers may also be provided. 24, 48 or 96 are the preferred number of reaction chambers since the reaction products generated are generally placed in vessels on a micro-titration plate. Conventional micro-titration plates have 96 reaction vessels so that, with 24, 48 or 96 reaction chambers, all the vessels of a micro-titration plate can be filled with synthesis products from one, two or four synthesising processes.

In a preferred embodiment of the present invention, a display unit with one window for each reaction chamber is provided. In each of these windows, a significant value for the quality of the synthesising process is displayed.

Provided for this purpose is an optical sensor51, mounted as close as possible to the reaction chambers3and the upper selector slider9. In the present embodiment the optical sensor51is mounted directly on an upper housing cover. However it is also possible to integrate the optical sensor in the selector slider9adjacent to the control orifice15. From the optical sensor51a line52leads to the metering pump (not shown) which is in the form of a suction pump. The optical sensor51detects the light transmittance (turbidity) of the intermediate or end product drawn from the reaction chambers3between each individual stage of the process.

By mounting the optical sensor51close to the selector slider9, a rapid response in the light intensity measurement is obtained, since the intermediate and end products produced in the reaction chambers have to be conveyed only a short distance before they can be detected by the sensor51. Moreover, with this arrangement of the sensor51, stray light is safely screened from the detection zone.

During oligonucleotide synthesis which is proceeding correctly, the intermediate products gradually become cloudy with each stage of reaction, due to an increase in the DMT content (DMT=dimethyl). In known oligonucleotide synthesis apparatus, the light intensity obtained at each stage is output as a numerical value. With several reaction chambers, this generates a corresponding number of columns of figures, resulting in an unmanageable number of numerical values after only a few process stages have elapsed.

With the apparatus according to the invention this large number of numerical values is avoided, since for each reaction chamber only one significant value for the quality of the current oligonucleotide synthesis is displayed.

This significant value for the quality of the current oligonucleotide synthesis may be e.g. the correlation coefficient R of the detected light intensities.

The correlation coefficient R is calculated in accordance with the following formula:R=m⁢⁢σiσs,
wherein s is the light intensity detected from a measurement and the individual measurements are counted by the numerator i, and σs, is the standard deviation of the measured values s, σithe standard deviation of the numerator i, and m the slope of the regression lines in a coordinate system in which the light intensity is plotted on the ordinate and the numerator on the abszisse.

The standard deviation σs, the standard deviation σ1and the slope m are calculated according to the following formulae:σs=∑N⁢s2-(∑N⁢s)2NN-1σi=∑N⁢i2-(∑N⁢i)2NN-1m=∑N⁢si-∑N⁢s⁢∑N⁢iN∑N⁢i2-(∑N⁢i)2N
wherein N is the total number of measured values.

In the coordinate system described above, when the oligonucleotide synthesis is proceeding correctly then, due to the gradual development of cloudiness, the light intensities will lie roughly on a slightly falling straight line. Only if there is a fault in the oligonucleotide synthesis will there be light intensity values deviating markedly from the straight line. The correlation coefficient R indicates how precisely the individual measured values lie on the straight line, wherein the correlation coefficient R may assume values between −1 and +1. If the correlation coefficient R is equal to 0, then a straight line can not be drawn through the measured values, whereas on the other hand with values of −1 or +1 of the correlation coefficient R, the measured values lie exactly on a straight line. Consequently the individual windows show the absolute value (R) of the respective correlation coefficient R assigned to a reaction chamber3so that an operator, in the event of a marked deviation from 1, immediately recognizes that the synthesis in the reaction chamber concerned is not proceeding correctly, without the need to monitor a column of figures or a large number of measured values.

In a preferred embodiment of the invention, the last respective measured values are more heavily weighted than the other measured values. For example, in calculation of the correlation coefficient R the number pair (measured value si, numerator i) is weighted as much as all other measured values together, i.e. the number pair of the last measured value sienters the calculation just as often as the other measured values, namely i−1 times. If the next measured value si+1is obtained, then the increased weighting of the measured value siis rescinded and the new measured value si+1is weighted i times.

Due to this higher weighting of the last respective measured value the correlation coefficient, thus modified, responds more quickly to a deviation from the straight line. This allows the operator to detect and react quickly to errors.

In a preferred arrangement, several apparatuses according to the invention, e.g. 3 to 20 and preferably 6 or 12, are combined into a single unit and provided with a common supply for reagents, gas and electrical power. Each of the storage vessels containing the reagents has a level indicator, so that their level may be monitored automatically by a level monitoring instrument. If a level is low, then the level monitoring instrument gives a signal to the operator indicating that the reagent concerned requires topping-up or that the relevant storage vessel requires replacement. This level monitoring instrument permits semi-automatic and continuous operation of this unit comprised of several synthesising apparatuses.

With this arrangement, the reagents are held in the storage vessels under pressure from a protective gas. This protective gas has two functions. It is intended to prevent the reagents from coming into contact with moisture-laden air since, through contact with moist air, undesired reactions could occur and impair the functioning of the reagents. In addition, the protective gas exerts a pressure which assists the feeding of the reagents to the reaction chambers3. Because of this, in drawing the reagents from the reaction chambers3, the suction pump can operate with less vacuum, thus making it possible to use reagents with low vapour pressure too.

Preferably annular seal inserts are used at all exits of orifices and bores of the sliders through which chemicals are fed. These seal inserts are made of a wear-resistant plastic, e.g. Teflon.

It is also possible for the sliders to be made of plastic. Suitable plastics are Teflon, Peek and Pom.

The invention is described above with the aid of embodiments with three sliders. Corresponding apparatuses with four or more sliders are known. The invention may also be applied to such apparatuses. A slider, for the purposes of the present application, is any sliding plate or disc or any sliding rod. The sliders according to the invention are discs rotatable around an axis of rotation.