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Plant Genetics: Pollen clusters
PRODUCT NEWS
Biomolecular interactions
Sample screening
IAsys from Fisons is an ideal system for studying biomolecular interactions in real time. A wide range of binding events and kinetic reaction rates can be analyzed in minutes, without the need for hazardous radio-labels, laborious purification procedures or tedious assay development. Protein-protein, protein-DNA, drug-receptor and antibody-antigen interactions, and even interactions involving cells and particulates, can be studied in a fraction of the time compared with conventional techniques. In IAsys, an optical biosensor is integrated into a stirred microcuvette sample cell, which overcomes the limitations associated with complex fluidics. Samples can be added directly into the micro-cuvette, allowing instant and complete control of experimental conditions. The ability to easily remove and re-insert the microcuvette maximises research productivity.
The new GeneAmp EZ rTth RNA PCR Kit from PerkinElmer is a research kit designed for rapid, sensitive and easy sample screening using RNA PCR. This kit utilizes both the reverse transcriptase and DNA polymerase activities of a single thermostable DNA polymerase, rTth DNA Polymerase. RNA PCR facilitates detection and analysis of gene expression at the RNA level, as well as detection of RNA species at very low copy numbers, such as cellular RNAs and viruses. The kit contains all the components required for reverse transcription of RNA to cDNA and subsequent amplification by the GeneAmp PCR process using a single enzyme, rTth DNA Polymerase, in a single reaction vessel and a single buffer system. The transition from reverse transcriptase activity to DNA polymerase activity takes place without buffer changes or subsequent reagent addition steps. The use of the thermoactive and thermostable enzyme, rTth DNA Polymerase, for both reverse transcription and PCR steps allows for increased specificity in primer binding as well as alleviation of problematic secondary structures in the RNA template.
Circle A on reader response card
Quality control
DNA isolation
Quality control demands a simple, fast and unambiguous check on a sample. The 265 Rheomat from Mettler Toledo is rugged and simple, and a quick sample change is possible. The precise measurement is followed by an evaluation that allows a clear-cut assessment of the sample according to individually selectable quality criteria. The minimum configuration of control unit, measurement system and printer allows single-point measurements, interval measurements or even the plotting of flow curves. The cone and plate measurement arrangement allows particularly rapid and simple handling and is suitable for the melting of all types of samples. The measuring temperature of the CP3 ranges from -200 C to 170C. Use of the SWR37 PC software offers additional ease of operation: a special quality control mode allows a measurement with subsequent evaluation to be performed fully automatically in a simple manner.
Stratagene has developed a rapid phenol/chloroform-free method for isolating pure DNA. This ClearCut miniprep kit requires only a microcentrifuge to process high-yield, small-scale plasmid preparations within 20 minutes. The kit can also be used to perform buffer exchanges and to remove primers and dNTPs from PCR + products in only 5 minutes. The ClearCut miniprep kit is used to bind the DNA, wash away the reaction components and elute the DNA in water/TE buffer. The DNA can then be used directly in restriction, ligation and sequencing reactions.
The Lasermat 2000 builds on the rapid mass analysis and simplicity of operation offered by the Lasermat, with significantly improved performance and automation capabilities. The speed and simplicity of matrixassisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry means that biochemists can have fast and accurate mass measurement in their own laboratory. Samples ranging from small peptides up to large glycoproteins over 200 kD can be easily measured. Simple software control and builtin automation make the Lasermat 2000 a reliable tool for use by all laboratory personnel.
Circle B on reader response card
Circle C on reader response card
Circle E on reader response card
Circle D on reader response card
Mass spectrometry
© Current Biology 1994, Vol 4 No 8
861
862
Current Biology 1994, Vol 4 No 9
.1In~
Oligo 5.0
Bcl-2 and apoptosis Oncogene Science have released a new antibody directed against bcl-2encoded proteins which have been shown to inhibit apoptosis. Apoptosis naturally occurs in cells during metamorphosis and homeostasis. bcl-2 (Ab-1), catalog # OP60, is a mouse monoclonal antibody that works in staining of frozen sections, paraffinembedded sections and cells. Circle F on reader response card
A-tailing kit It is possible to insert a PCR-generated DNA fragment with any type of end base into T-vectors using Amersham's new A-Tailing kit. Any polymerase can be used for PCR product cloning. The A-Tailing kit includes all reagents necessary to generate a 3' blunt end and then selectively add the 3' adenosine residue - all without the need for DNA precipitation. Circle G on reader response card
Barrier pipette tips
Disposable aerosol-barrier tips are now available from Beckman Instruments, Inc. for the Biomek Laboratory Automation Workstation. These polypropylene tips contain a specially designed polystyrene plug that is inserted prior to sterilization. The polystyrene acts as an effective barrier to aerosols, and is non-wicking if contacted by aqueous fluids. These disposable, aerosol-barrier tips reduce the risk of sample carry-over by aerosols, and are beneficial to those working with biohazardous or radioactive materials. They are available for volumes from 1ml to 125 ml. Circle H on reader response card
Adsorber gel Boehringer Mannheim's new detergent adsorber gel removes virtually any detergent from sample solutions. The high binding-capacity of the detergent adsorber gel enables the detergent's removal in a very short time. The sample is immediately ready for further treatments or experiments. The low affinity of the detergent adsorber gel to proteins ensures high recovery of the valuable proteins. Circle I on reader response card
National Biosciences, Inc. (NBI) announces version 5.0 of the Oligo primer analysis software for Windows. This new Windows version provides powerful new functions to assist researchers in the selection of optimal oligonucleotides for PCR, sequencing, hybridizations and other applications. These include a multiplex primer selection, sortable primer pair tables, inverse PCR, 5' GC clamp, and enhanced false priming and specificity checks. Other new features of Oligo include: LCR analysis, specialized searches for sequencing primers and hybridization probes, hybridization time calculations, back translation capabilities, and a unique oligo database and ordering form. In addition to the Oligo program, NBI's broad software product line includes programs for DNA and protein sequence analysis, molecular modeling, genetic pedigree drawing/data management and analysis, human genome mapping and multiple sequence alignment.
LDL assay Genzyme Diagnostics has now introduced a direct assay to measure LDL. Using a special immunoseparation technology developed by Genzyme, the Direct LDL kit utilizes a cocktail of polyclonal antibodies to selectively remove the other cholesterol particles, such as HDL and VLDL, from the sample. LDL can then be determined using any standardized cholesterol assay. The results obtained correlate very well with the accepted reference method, ultracentrifugation, and are unaffected by high triglyceride levels. Genzyme's Direct LDL kit is simple to use and is unbiased by high triglyceride levels, removing the need for patients to fast for 12 hours prior to sample collection. Circle L on reader response card
PCR reactor
Labsystems have developed Forma software for blood grouping and haemagglutination, providing a highly flexible and comprehensive data reduction package for use with the Multiskan and iEMS range of microplate readers. It is suitable for use in all aspects of microplate blood grouping and haemagglutination, including ABO rhesus typing, red cell phenotyping, antibody screening and identification, and haemagglutination.
The new polymerase chain reactor from Stuart Scientific, the SPCR3 Mini-Gene, is designed to accommodate small numbers of samples. Depending on the choice of heating block, it accepts up to 15 x 0.5 ml tubes, one small microtitre plate (8 x 4 hole format), 4 x 8 strips of 0.2 ml tubes or 32 x 0.2 ml tubes. With its built-in peltier thermoelectric refrigeration, it operates very rapidly with a peak heating rate of 1.8 0 C per second and peak cooling rate of 1.2 0 C per second, over a temperature range from 4C to 99C. Temperature uniformity is 0.2 0 C and there is no precision sacrificed at the cut-off temperatures through over- or under-shooting.
Circle K on reader response card
Circle M on reader response card
Circle J on reader response card
Microplate reader
Current Biology Instructions to authors of Research Papers
Scope Current Biology publishes research papers in any area of biology, provided that the research clearly represents an important advance of especially broad interest to biologists. Papers must be written and illustrated in a way that is appropriate for nonspecialist readers. Papers should normally occupy 2-10 pages of the journal; there are about 1 000 words or 35 references to a fll page. Reviewing and publication speed All submissions will be subject to an immediate editorial screening process, usually in consultation with members of the editorial board. Those that meet the criteria for consideration, as outlined above, will normally be sent to two reviewers who have agreed in advance to assess the paper rapidly, and the editors will make every effort to reach decisions on these papers within three weeks of the date of receipt. Accepted papers will be typeset within three days if provided on a disc. Papers will be published in the next issue to go to press after proofs have been returned. Submission Enquiries as to the suitability of a potential submission can be made in advance by fax to +44 (0)71 580 8167 or by e-mail to [email protected], in which case an abstract of the paper that makes clear how it advances knowledge must be provided. Four copies of the manuscript should be submitted, preferably with a disc (see below), to: the Editors, Current Biology, 34-42 Cleveland Street, London WIP 5FB, UK. Please provide telephone and fax numbers, and an e-mail address if available. Suggestions for reviewers are welcome. There are no handling charges, no page charges and no charges for colour illustrations (see Illustrations). Manuscript preparation All text must be double-spaced throughout. All pages must be numbered. Abbreviations should be defined on first usage, and a list of all abbreviations used should be provided. Spelling may be British or American, but not a mixture. Manuscript organization Manuscripts should be divided into the following sections: Title page: should list names and addresses of all authors and should indicate the corresponding author. A running head of not more than 40 characters, including spaces, should be provided. Abstract: should not exceed 250 words and must be structured into sections: Background, Results, Conclusions. Background: must be written from the standpoint of nonspecialists, must clearly state (and, if helpful, illustrate) the background to the research and its aims. Results and Discussion: may be combined or kept separate, and may be broken into subsections. Conclusions: must state clearly the main conclusions of the research and give an explanation of their importance. Materials and methods: should be subdivided. Acknowledgements: should be kept to a minimum. Figure legends: should start with a title and should not exceed one page of text. Tables: should be titled and should not include vertical rules. Units: should be SI throughout (except litre and molar). References: must be cited consecutively, in square brackets, in the text, followed by any that occur only in the tables or legends. Only papers that have been published or are in press may be included in the reference list; submitted manuscripts, personal communications (which can be included only with permission), abstracts and unpublished data should be mentioned in the text.
Journal abbreviations follow Index Medicus/Medline; name up to six authors, followed by et al. if more. Example of Current Biology reference: 1.
Holmes S, Watson : Identification of the function of the moriarty gene product. Curr Biol 1992, 3:121-129.
Illustrations Introductory and/or summary illustrations are encouraged and we can assist in preparation of artwork for manuscripts accepted for publication. Some redrawing and/or colouring of figures may be suggested. Colour should be used only to enhance understanding, in which case it will not be charged for. Figures should be 84 mm wide (single column), wherever possible. Photographs should be provided with a scale bar, if appropriate. Text, arrows, etc. should not be pasted directly on to photographs; instead, their position should be indicated on a photocopy. For illustrations on disc, see Disc preparation. Disc preparation It will greatly assist rapid publication if manuscripts can be typeset directly from authors' floppy discs. We can accept most word-processor programs, in both PC (including Windows) and Macintosh formats. With the latter, please use 'Save as' and select MSDOS file format if the option is available. In all cases, also save the text as an ASCII file in case the word processing file is not translatable. Label the disc with the authors' names, the word processing program and version used, and the type of computer. In the case of a discrepancy between the disc and the manuscript, the latter will be taken as the definitive version. To avoid problems, please take special care on disc to: * type the text unjustified, without hyphenating words at line breaks * use carriage returns only to end headings and paragraphs, not to rearrange lines * avoid including page numbers or other running material · follow the precise style of Current Biology's references * use the ASCII character set if possible for special characters (e.g. Greek letters and mathematical symbols) With illustrations on disc, we can accept application files from the following graphics packages: for PC: CoreIDRAW (2, 3 or 4), Adobe Illustrator and Freehand; for other PC packages, save the file in Adobe Illustrator format, or call for advice. For Macintosh: Adobe Illustrator or Freehand; for other Mac packages: save in Adobe Illustrator (88, 1.1 or 3.0) format. Label all discs with the authors' names and details of the format of any illustration files. Please always provide a hard copy to accompany the disc; the hard copy will be taken as the definitive version. Proofs For clarity when faxing, please number your corrections on the proofs, and also list them on an accompanying sheet. Offprints/reprints 25 free offprints will be provided for each paper. Extra offprints can be ordered before the press date. Reprints may be purchased at a later stage. Policies Publication in Current Biology implies that all authors of the paper have read and agreed to its content, and that readily replaceable material described in the paper will be freely distributed to academic colleagues. Nucleic-acid and protein sequences and crystal coordinates should be deposited in an appropriate databank in time for the accession number to be included in the paper. 863
Biomolecular interactions
Sample screening
IAsys from Fisons is an ideal system for studying biomolecular interactions in real time. A wide range of binding events and kinetic reaction rates can be analyzed in minutes, without the need for hazardous radio-labels, laborious purification procedures or tedious assay development. Protein-protein, protein-DNA, drug-receptor and antibody-antigen interactions, and even interactions involving cells and particulates, can be studied in a fraction of the time compared with conventional techniques. In IAsys, an optical biosensor is integrated into a stirred microcuvette sample cell, which overcomes the limitations associated with complex fluidics. Samples can be added directly into the micro-cuvette, allowing instant and complete control of experimental conditions. The ability to easily remove and re-insert the microcuvette maximises research productivity.
The new GeneAmp EZ rTth RNA PCR Kit from PerkinElmer is a research kit designed for rapid, sensitive and easy sample screening using RNA PCR. This kit utilizes both the reverse transcriptase and DNA polymerase activities of a single thermostable DNA polymerase, rTth DNA Polymerase. RNA PCR facilitates detection and analysis of gene expression at the RNA level, as well as detection of RNA species at very low copy numbers, such as cellular RNAs and viruses. The kit contains all the components required for reverse transcription of RNA to cDNA and subsequent amplification by the GeneAmp PCR process using a single enzyme, rTth DNA Polymerase, in a single reaction vessel and a single buffer system. The transition from reverse transcriptase activity to DNA polymerase activity takes place without buffer changes or subsequent reagent addition steps. The use of the thermoactive and thermostable enzyme, rTth DNA Polymerase, for both reverse transcription and PCR steps allows for increased specificity in primer binding as well as alleviation of problematic secondary structures in the RNA template.
Circle A on reader response card
Quality control
DNA isolation
Quality control demands a simple, fast and unambiguous check on a sample. The 265 Rheomat from Mettler Toledo is rugged and simple, and a quick sample change is possible. The precise measurement is followed by an evaluation that allows a clear-cut assessment of the sample according to individually selectable quality criteria. The minimum configuration of control unit, measurement system and printer allows single-point measurements, interval measurements or even the plotting of flow curves. The cone and plate measurement arrangement allows particularly rapid and simple handling and is suitable for the melting of all types of samples. The measuring temperature of the CP3 ranges from -200 C to 170C. Use of the SWR37 PC software offers additional ease of operation: a special quality control mode allows a measurement with subsequent evaluation to be performed fully automatically in a simple manner.
Stratagene has developed a rapid phenol/chloroform-free method for isolating pure DNA. This ClearCut miniprep kit requires only a microcentrifuge to process high-yield, small-scale plasmid preparations within 20 minutes. The kit can also be used to perform buffer exchanges and to remove primers and dNTPs from PCR + products in only 5 minutes. The ClearCut miniprep kit is used to bind the DNA, wash away the reaction components and elute the DNA in water/TE buffer. The DNA can then be used directly in restriction, ligation and sequencing reactions.
The Lasermat 2000 builds on the rapid mass analysis and simplicity of operation offered by the Lasermat, with significantly improved performance and automation capabilities. The speed and simplicity of matrixassisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry means that biochemists can have fast and accurate mass measurement in their own laboratory. Samples ranging from small peptides up to large glycoproteins over 200 kD can be easily measured. Simple software control and builtin automation make the Lasermat 2000 a reliable tool for use by all laboratory personnel.
Circle B on reader response card
Circle C on reader response card
Circle E on reader response card
Circle D on reader response card
Mass spectrometry
© Current Biology 1994, Vol 4 No 8
861
862
Current Biology 1994, Vol 4 No 9
.1In~
Oligo 5.0
Bcl-2 and apoptosis Oncogene Science have released a new antibody directed against bcl-2encoded proteins which have been shown to inhibit apoptosis. Apoptosis naturally occurs in cells during metamorphosis and homeostasis. bcl-2 (Ab-1), catalog # OP60, is a mouse monoclonal antibody that works in staining of frozen sections, paraffinembedded sections and cells. Circle F on reader response card
A-tailing kit It is possible to insert a PCR-generated DNA fragment with any type of end base into T-vectors using Amersham's new A-Tailing kit. Any polymerase can be used for PCR product cloning. The A-Tailing kit includes all reagents necessary to generate a 3' blunt end and then selectively add the 3' adenosine residue - all without the need for DNA precipitation. Circle G on reader response card
Barrier pipette tips
Disposable aerosol-barrier tips are now available from Beckman Instruments, Inc. for the Biomek Laboratory Automation Workstation. These polypropylene tips contain a specially designed polystyrene plug that is inserted prior to sterilization. The polystyrene acts as an effective barrier to aerosols, and is non-wicking if contacted by aqueous fluids. These disposable, aerosol-barrier tips reduce the risk of sample carry-over by aerosols, and are beneficial to those working with biohazardous or radioactive materials. They are available for volumes from 1ml to 125 ml. Circle H on reader response card
Adsorber gel Boehringer Mannheim's new detergent adsorber gel removes virtually any detergent from sample solutions. The high binding-capacity of the detergent adsorber gel enables the detergent's removal in a very short time. The sample is immediately ready for further treatments or experiments. The low affinity of the detergent adsorber gel to proteins ensures high recovery of the valuable proteins. Circle I on reader response card
National Biosciences, Inc. (NBI) announces version 5.0 of the Oligo primer analysis software for Windows. This new Windows version provides powerful new functions to assist researchers in the selection of optimal oligonucleotides for PCR, sequencing, hybridizations and other applications. These include a multiplex primer selection, sortable primer pair tables, inverse PCR, 5' GC clamp, and enhanced false priming and specificity checks. Other new features of Oligo include: LCR analysis, specialized searches for sequencing primers and hybridization probes, hybridization time calculations, back translation capabilities, and a unique oligo database and ordering form. In addition to the Oligo program, NBI's broad software product line includes programs for DNA and protein sequence analysis, molecular modeling, genetic pedigree drawing/data management and analysis, human genome mapping and multiple sequence alignment.
LDL assay Genzyme Diagnostics has now introduced a direct assay to measure LDL. Using a special immunoseparation technology developed by Genzyme, the Direct LDL kit utilizes a cocktail of polyclonal antibodies to selectively remove the other cholesterol particles, such as HDL and VLDL, from the sample. LDL can then be determined using any standardized cholesterol assay. The results obtained correlate very well with the accepted reference method, ultracentrifugation, and are unaffected by high triglyceride levels. Genzyme's Direct LDL kit is simple to use and is unbiased by high triglyceride levels, removing the need for patients to fast for 12 hours prior to sample collection. Circle L on reader response card
PCR reactor
Labsystems have developed Forma software for blood grouping and haemagglutination, providing a highly flexible and comprehensive data reduction package for use with the Multiskan and iEMS range of microplate readers. It is suitable for use in all aspects of microplate blood grouping and haemagglutination, including ABO rhesus typing, red cell phenotyping, antibody screening and identification, and haemagglutination.
The new polymerase chain reactor from Stuart Scientific, the SPCR3 Mini-Gene, is designed to accommodate small numbers of samples. Depending on the choice of heating block, it accepts up to 15 x 0.5 ml tubes, one small microtitre plate (8 x 4 hole format), 4 x 8 strips of 0.2 ml tubes or 32 x 0.2 ml tubes. With its built-in peltier thermoelectric refrigeration, it operates very rapidly with a peak heating rate of 1.8 0 C per second and peak cooling rate of 1.2 0 C per second, over a temperature range from 4C to 99C. Temperature uniformity is 0.2 0 C and there is no precision sacrificed at the cut-off temperatures through over- or under-shooting.
Circle K on reader response card
Circle M on reader response card
Circle J on reader response card
Microplate reader
Current Biology Instructions to authors of Research Papers
Scope Current Biology publishes research papers in any area of biology, provided that the research clearly represents an important advance of especially broad interest to biologists. Papers must be written and illustrated in a way that is appropriate for nonspecialist readers. Papers should normally occupy 2-10 pages of the journal; there are about 1 000 words or 35 references to a fll page. Reviewing and publication speed All submissions will be subject to an immediate editorial screening process, usually in consultation with members of the editorial board. Those that meet the criteria for consideration, as outlined above, will normally be sent to two reviewers who have agreed in advance to assess the paper rapidly, and the editors will make every effort to reach decisions on these papers within three weeks of the date of receipt. Accepted papers will be typeset within three days if provided on a disc. Papers will be published in the next issue to go to press after proofs have been returned. Submission Enquiries as to the suitability of a potential submission can be made in advance by fax to +44 (0)71 580 8167 or by e-mail to [email protected], in which case an abstract of the paper that makes clear how it advances knowledge must be provided. Four copies of the manuscript should be submitted, preferably with a disc (see below), to: the Editors, Current Biology, 34-42 Cleveland Street, London WIP 5FB, UK. Please provide telephone and fax numbers, and an e-mail address if available. Suggestions for reviewers are welcome. There are no handling charges, no page charges and no charges for colour illustrations (see Illustrations). Manuscript preparation All text must be double-spaced throughout. All pages must be numbered. Abbreviations should be defined on first usage, and a list of all abbreviations used should be provided. Spelling may be British or American, but not a mixture. Manuscript organization Manuscripts should be divided into the following sections: Title page: should list names and addresses of all authors and should indicate the corresponding author. A running head of not more than 40 characters, including spaces, should be provided. Abstract: should not exceed 250 words and must be structured into sections: Background, Results, Conclusions. Background: must be written from the standpoint of nonspecialists, must clearly state (and, if helpful, illustrate) the background to the research and its aims. Results and Discussion: may be combined or kept separate, and may be broken into subsections. Conclusions: must state clearly the main conclusions of the research and give an explanation of their importance. Materials and methods: should be subdivided. Acknowledgements: should be kept to a minimum. Figure legends: should start with a title and should not exceed one page of text. Tables: should be titled and should not include vertical rules. Units: should be SI throughout (except litre and molar). References: must be cited consecutively, in square brackets, in the text, followed by any that occur only in the tables or legends. Only papers that have been published or are in press may be included in the reference list; submitted manuscripts, personal communications (which can be included only with permission), abstracts and unpublished data should be mentioned in the text.
Journal abbreviations follow Index Medicus/Medline; name up to six authors, followed by et al. if more. Example of Current Biology reference: 1.
Holmes S, Watson : Identification of the function of the moriarty gene product. Curr Biol 1992, 3:121-129.
Illustrations Introductory and/or summary illustrations are encouraged and we can assist in preparation of artwork for manuscripts accepted for publication. Some redrawing and/or colouring of figures may be suggested. Colour should be used only to enhance understanding, in which case it will not be charged for. Figures should be 84 mm wide (single column), wherever possible. Photographs should be provided with a scale bar, if appropriate. Text, arrows, etc. should not be pasted directly on to photographs; instead, their position should be indicated on a photocopy. For illustrations on disc, see Disc preparation. Disc preparation It will greatly assist rapid publication if manuscripts can be typeset directly from authors' floppy discs. We can accept most word-processor programs, in both PC (including Windows) and Macintosh formats. With the latter, please use 'Save as' and select MSDOS file format if the option is available. In all cases, also save the text as an ASCII file in case the word processing file is not translatable. Label the disc with the authors' names, the word processing program and version used, and the type of computer. In the case of a discrepancy between the disc and the manuscript, the latter will be taken as the definitive version. To avoid problems, please take special care on disc to: * type the text unjustified, without hyphenating words at line breaks * use carriage returns only to end headings and paragraphs, not to rearrange lines * avoid including page numbers or other running material · follow the precise style of Current Biology's references * use the ASCII character set if possible for special characters (e.g. Greek letters and mathematical symbols) With illustrations on disc, we can accept application files from the following graphics packages: for PC: CoreIDRAW (2, 3 or 4), Adobe Illustrator and Freehand; for other PC packages, save the file in Adobe Illustrator format, or call for advice. For Macintosh: Adobe Illustrator or Freehand; for other Mac packages: save in Adobe Illustrator (88, 1.1 or 3.0) format. Label all discs with the authors' names and details of the format of any illustration files. Please always provide a hard copy to accompany the disc; the hard copy will be taken as the definitive version. Proofs For clarity when faxing, please number your corrections on the proofs, and also list them on an accompanying sheet. Offprints/reprints 25 free offprints will be provided for each paper. Extra offprints can be ordered before the press date. Reprints may be purchased at a later stage. Policies Publication in Current Biology implies that all authors of the paper have read and agreed to its content, and that readily replaceable material described in the paper will be freely distributed to academic colleagues. Nucleic-acid and protein sequences and crystal coordinates should be deposited in an appropriate databank in time for the accession number to be included in the paper. 863