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Lawson CP, Füchtbauer AF, Wranne MS, Giraud T, Floyd T, Dumat B, Andersen NK, H El-Sagheer A, Brown T, Gradén H, Wilhelmsson LM, Grøtli M. Synthesis, oligonucleotide incorporation and fluorescence properties in DNA of a bicyclic thymine analogue. Sci Rep 2018; 8:13970. [PMID: 30228309 PMCID: PMC6143597 DOI: 10.1038/s41598-018-31897-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 08/23/2018] [Indexed: 12/26/2022] Open
Abstract
Fluorescent base analogues (FBAs) have emerged as a powerful class of molecular reporters of location and environment for nucleic acids. In our overall mission to develop bright and useful FBAs for all natural nucleobases, herein we describe the synthesis and thorough characterization of bicyclic thymidine (bT), both as a monomer and when incorporated into DNA. We have developed a robust synthetic route for the preparation of the bT DNA monomer and the corresponding protected phosphoramidite for solid-phase DNA synthesis. The bT deoxyribonucleoside has a brightness value of 790 M−1cm−1 in water, which is comparable or higher than most fluorescent thymine analogues reported. When incorporated into DNA, bT pairs selectively with adenine without perturbing the B-form structure, keeping the melting thermodynamics of the B-form duplex DNA virtually unchanged. As for most fluorescent base analogues, the emission of bT is reduced inside DNA (4.5- and 13-fold in single- and double-stranded DNA, respectively). Overall, these properties make bT an interesting thymine analogue for studying DNA and an excellent starting point for the development of brighter bT derivatives.
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Affiliation(s)
- Christopher P Lawson
- Department of Chemistry and Molecular Biology, University of Gothenburg, S-41296, Gothenburg, Sweden
| | - Anders F Füchtbauer
- Department of Chemistry and Chemical Engineering, Chemistry and Biochemistry, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden
| | - Moa S Wranne
- Department of Chemistry and Chemical Engineering, Chemistry and Biochemistry, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden
| | - Tristan Giraud
- Department of Chemistry and Chemical Engineering, Chemistry and Biochemistry, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden
| | - Thomas Floyd
- Department of Chemistry and Chemical Engineering, Chemistry and Biochemistry, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden
| | - Blaise Dumat
- Department of Chemistry and Chemical Engineering, Chemistry and Biochemistry, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden
| | - Nicolai K Andersen
- Department of Chemistry and Chemical Engineering, Chemistry and Biochemistry, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden
| | - Afaf H El-Sagheer
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA, UK.,Chemistry Branch, Department of Science and Mathematics, Faculty of Petroleum and Mining Engineering, Suez University, Suez, 43721, Egypt
| | - Tom Brown
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA, UK
| | - Henrik Gradén
- Cardiovascular, Renal and Metabolic Diseases IMED Biotech Unit, AstraZeneca Gothenburg, Pepparedsleden 1, Molndal, SE-431 83, Sweden
| | - L Marcus Wilhelmsson
- Department of Chemistry and Chemical Engineering, Chemistry and Biochemistry, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden.
| | - Morten Grøtli
- Department of Chemistry and Molecular Biology, University of Gothenburg, S-41296, Gothenburg, Sweden.
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2
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Geny S, Moreno PMD, Krzywkowski T, Gissberg O, Andersen NK, Isse AJ, El-Madani AM, Lou C, Pabon YV, Anderson BA, Zaghloul EM, Zain R, Hrdlicka PJ, Jørgensen PT, Nilsson M, Lundin KE, Pedersen EB, Wengel J, Smith CIE. Next-generation bis-locked nucleic acids with stacking linker and 2'-glycylamino-LNA show enhanced DNA invasion into supercoiled duplexes. Nucleic Acids Res 2016; 44:2007-19. [PMID: 26857548 PMCID: PMC4797291 DOI: 10.1093/nar/gkw021] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 01/08/2016] [Indexed: 12/17/2022] Open
Abstract
Targeting and invading double-stranded DNA with synthetic oligonucleotides under physiological conditions remain a challenge. Bis-locked nucleic acids (bisLNAs) are clamp-forming oligonucleotides able to invade into supercoiled DNA via combined Hoogsteen and Watson–Crick binding. To improve the bisLNA design, we investigated its mechanism of binding. Our results suggest that bisLNAs bind via Hoogsteen-arm first, followed by Watson–Crick arm invasion, initiated at the tail. Based on this proposed hybridization mechanism, we designed next-generation bisLNAs with a novel linker able to stack to adjacent nucleobases, a new strategy previously not applied for any type of clamp-constructs. Although the Hoogsteen-arm limits the invasion, upon incorporation of the stacking linker, bisLNA invasion is significantly more efficient than for non-clamp, or nucleotide-linker containing LNA-constructs. Further improvements were obtained by substituting LNA with 2′-glycylamino-LNA, contributing a positive charge. For regular bisLNAs a 14-nt tail significantly enhances invasion. However, when two stacking linkers were incorporated, tail-less bisLNAs were able to efficiently invade. Finally, successful targeting of plasmids inside bacteria clearly demonstrates that strand invasion can take place in a biologically relevant context.
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Affiliation(s)
- Sylvain Geny
- Department of Laboratory Medicine, Karolinska Institutet and Clinical Research Center, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden
| | - Pedro M D Moreno
- Department of Laboratory Medicine, Karolinska Institutet and Clinical Research Center, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden INEB-Instituto de Engenharia Biomedica, Universidade do Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal
| | - Tomasz Krzywkowski
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Stockholm, SE-171 21, Sweden
| | - Olof Gissberg
- Department of Laboratory Medicine, Karolinska Institutet and Clinical Research Center, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden
| | - Nicolai K Andersen
- Nucleic Acid Center, Department of Physics, Chemistry and Pharmacy, Nucleic Acid Centre, University of Southern Denmark, 5230 Odense, Denmark
| | - Abdirisaq J Isse
- Nucleic Acid Center, Department of Physics, Chemistry and Pharmacy, Nucleic Acid Centre, University of Southern Denmark, 5230 Odense, Denmark
| | - Amro M El-Madani
- Nucleic Acid Center, Department of Physics, Chemistry and Pharmacy, Nucleic Acid Centre, University of Southern Denmark, 5230 Odense, Denmark
| | - Chenguang Lou
- Nucleic Acid Center, Department of Physics, Chemistry and Pharmacy, Nucleic Acid Centre, University of Southern Denmark, 5230 Odense, Denmark
| | - Y Vladimir Pabon
- Department of Laboratory Medicine, Karolinska Institutet and Clinical Research Center, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden
| | | | - Eman M Zaghloul
- Department of Laboratory Medicine, Karolinska Institutet and Clinical Research Center, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden
| | - Rula Zain
- Department of Laboratory Medicine, Karolinska Institutet and Clinical Research Center, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden Centre for Rare Diseases, Department of Clinical Genetics, Karolinska University Hospital, SE-171 76 Stockholm, Sweden
| | | | - Per T Jørgensen
- Nucleic Acid Center, Department of Physics, Chemistry and Pharmacy, Nucleic Acid Centre, University of Southern Denmark, 5230 Odense, Denmark
| | - Mats Nilsson
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Stockholm, SE-171 21, Sweden
| | - Karin E Lundin
- Department of Laboratory Medicine, Karolinska Institutet and Clinical Research Center, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden
| | - Erik B Pedersen
- Nucleic Acid Center, Department of Physics, Chemistry and Pharmacy, Nucleic Acid Centre, University of Southern Denmark, 5230 Odense, Denmark
| | - Jesper Wengel
- Nucleic Acid Center, Department of Physics, Chemistry and Pharmacy, Nucleic Acid Centre, University of Southern Denmark, 5230 Odense, Denmark
| | - C I Edvard Smith
- Department of Laboratory Medicine, Karolinska Institutet and Clinical Research Center, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden
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3
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Dalager M, Andersen NK, Kumar P, Nielsen P, Sharma PK. Double-headed nucleotides introducing thymine nucleobases in the major groove of nucleic acid duplexes. Org Biomol Chem 2015; 13:7040-9. [PMID: 26053231 DOI: 10.1039/c5ob00872g] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Four different double-headed nucleosides each combining two thymine nucleobases with different linkers were synthesised. The 5-position of 2'-deoxyuridine was connected to the N1-position of a thymine through either m- or p-disubstituted phenyl or phenylacetylene linkers by the use of Suzuki or Sonogashira couplings. When introduced into oligonucleotides, the thermal stability of dsDNA and DNA : RNA duplexes were determined and structural information was obtained from CD- and fluorescence spectroscopy. Also the recognition of abasic sites was studied. In general, the more stable duplexes were obtained with m- rather than p-substitution and with phenylacetylene rather than phenyl linkers.
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Affiliation(s)
- Michael Dalager
- Nucleic Acid Center, Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, 5230 Odense M, Denmark.
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4
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Andersen NK, Anderson BA, Wengel J, Hrdlicka PJ. Synthesis and characterization of oligodeoxyribonucleotides modified with 2'-amino-α-L-LNA adenine monomers: high-affinity targeting of single-stranded DNA. J Org Chem 2013; 78:12690-702. [PMID: 24304240 DOI: 10.1021/jo4022937] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The development of conformationally restricted nucleotide building blocks continues to attract considerable interest because of their successful use within antisense, antigene, and other gene-targeting strategies. Locked nucleic acid (LNA) and its diastereomer α-L-LNA are two interesting examples thereof. Oligonucleotides modified with these units display greatly increased affinity toward nucleic acid targets, improved binding specificity, and enhanced enzymatic stability relative to unmodified strands. Here we present the synthesis and biophysical characterization of oligodeoxyribonucleotides (ONs) modified with 2'-amino-α-L-LNA adenine monomers W-Z. The synthesis of the target phosphoramidites 1-4 is initiated from pentafuranose 5, which upon Vorbrüggen glycosylation, O2'-deacylation, O2'-activation and C2'-azide introduction yields nucleoside 8. A one-pot tandem Staudinger/intramolecular nucleophilic substitution converts 8 into 2'-amino-α-L-LNA adenine intermediate 9, which after a series of nontrivial protecting-group manipulations affords key intermediate 15. Subsequent chemoselective N2'-functionalization and O3'-phosphitylation give targets 1-4 in ~1-3% overall yield over 11 steps from 5. ONs modified with pyrene-functionalized 2'-amino-α-L-LNA adenine monomers X-Z display greatly increased affinity toward DNA targets (ΔTm/modification up to +14 °C). Results from absorption and fluorescence spectroscopy suggest that the duplex stabilization is a result of pyrene intercalation. These characteristics render N2'-pyrene-functionalized 2'-amino-α-L-LNAs of considerable interest for DNA-targeting applications.
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Affiliation(s)
- Nicolai K Andersen
- Nucleic Acid Center, Department of Physics, Chemistry and Pharmacy, University of Southern Denmark , 5230 Odense, Denmark
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5
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Sau SP, Madsen AS, Podbevsek P, Andersen NK, Kumar TS, Andersen S, Rathje RL, Anderson BA, Guenther DC, Karmakar S, Kumar P, Plavec J, Wengel J, Hrdlicka PJ. Identification and characterization of second-generation invader locked nucleic acids (LNAs) for mixed-sequence recognition of double-stranded DNA. J Org Chem 2013; 78:9560-70. [PMID: 24032477 PMCID: PMC3833467 DOI: 10.1021/jo4015936] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The development of synthetic agents that recognize double-stranded DNA (dsDNA) is a long-standing goal that is inspired by the promise for tools that detect, regulate, and modify genes. Progress has been made with triplex-forming oligonucleotides, peptide nucleic acids, and polyamides, but substantial efforts are currently devoted to the development of alternative strategies that overcome the limitations observed with the classic approaches. In 2005, we introduced Invader locked nucleic acids (LNAs), i.e., double-stranded probes that are activated for mixed-sequence recognition of dsDNA through modification with "+1 interstrand zippers" of 2'-N-(pyren-1-yl)methyl-2'-amino-α-l-LNA monomers. Despite promising preliminary results, progress has been slow because of the synthetic complexity of the building blocks. Here we describe a study that led to the identification of two simpler classes of Invader monomers. We compare the thermal denaturation characteristics of double-stranded probes featuring different interstrand zippers of pyrene-functionalized monomers based on 2'-amino-α-l-LNA, 2'-N-methyl-2'-amino-DNA, and RNA scaffolds. Insights from fluorescence spectroscopy, molecular modeling, and NMR spectroscopy are used to elucidate the structural factors that govern probe activation. We demonstrate that probes with +1 zippers of 2'-O-(pyren-1-yl)methyl-RNA or 2'-N-methyl-2'-N-(pyren-1-yl)methyl-2'-amino-DNA monomers recognize DNA hairpins with similar efficiency as original Invader LNAs. Access to synthetically simple monomers will accelerate the use of Invader-mediated dsDNA recognition for applications in molecular biology and nucleic acid diagnostics.
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Affiliation(s)
- Sujay P. Sau
- Department of Chemistry, University of Idaho, Moscow, ID-83844, USA
| | - Andreas S. Madsen
- Nucleic Acid Center, Department of Physics and Chemistry, University of Southern Denmark, Odense, Denmark
| | | | - Nicolai K. Andersen
- Nucleic Acid Center, Department of Physics and Chemistry, University of Southern Denmark, Odense, Denmark
| | - T. Santhosh Kumar
- Nucleic Acid Center, Department of Physics and Chemistry, University of Southern Denmark, Odense, Denmark
| | - Sanne Andersen
- Department of Chemistry, University of Idaho, Moscow, ID-83844, USA
- Nucleic Acid Center, Department of Physics and Chemistry, University of Southern Denmark, Odense, Denmark
| | - Rie L. Rathje
- Department of Chemistry, University of Idaho, Moscow, ID-83844, USA
- Nucleic Acid Center, Department of Physics and Chemistry, University of Southern Denmark, Odense, Denmark
| | | | - Dale C. Guenther
- Department of Chemistry, University of Idaho, Moscow, ID-83844, USA
| | - Saswata Karmakar
- Department of Chemistry, University of Idaho, Moscow, ID-83844, USA
| | - Pawan Kumar
- Department of Chemistry, University of Idaho, Moscow, ID-83844, USA
| | - Janez Plavec
- National Institute of Chemistry, Ljubljana, Slovenia
| | - Jesper Wengel
- Nucleic Acid Center, Department of Physics and Chemistry, University of Southern Denmark, Odense, Denmark
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Ravn LS, Andersen NK, Rasmussen MA, Christensen M, Edwards SA, Guy JH, Henckel P, Harrison AP. De electricitatis catholici musculari - Concerning the electrical properties of muscles, with emphasis on meat quality. Meat Sci 2008; 80:423-30. [PMID: 22063349 DOI: 10.1016/j.meatsci.2008.01.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2007] [Revised: 01/15/2008] [Accepted: 01/16/2008] [Indexed: 11/19/2022]
Abstract
This study aims to explore the potential of evoked non-invasive surface electromyography (SEMG) analysis, in predicting meat quality traits in livestock. Evoked SEMG is a system that records, transdermally, electrical signals generated in muscle fibres upon external stimulation. These signals are reported as compound muscle action potentials (CMAP). CMAP parameters of LD correlated negatively and significantly to ultimate pH (pH 24h) at day 61, but not at day 153 after birth, and a similar albeit positive correlation was observed for muscle glycogen content. Muscle glycogen content and pH 24h correlated negatively in LD and BF. Negative significant correlations between CMAP parameters and shear force were found in LD at day 153 after birth, which might, in the range of the recording electrodes, reflect the combined effect of large cross-sectional area fibres and reduced perimysium content per unit volume of muscle. The fact that correlations between CMAP characteristics and quality traits of both metabolic and non metabolic origin could be established, warrants a fuller investigation of this method in terms of its potential as a predictive tool for meat quality traits in live animals.
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Affiliation(s)
- L S Ravn
- Department of Animal and Veterinary Basic Sciences, Faculty of Life Sciences, University of Copenhagen, Grønnegårdsvej 7, 1870 Frederiksberg C, Denmark
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7
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Andersen NK, Wengel J, Hrdlicka PJ. N2'-functionalized 2'-amino-alpha-L-LNA adenine derivatives--efficient targeting of single stranded DNA. Nucleosides Nucleotides Nucleic Acids 2008; 26:1415-7. [PMID: 18066795 DOI: 10.1080/15257770701539153] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The synthesis of two pyrene-functionalized 2'-amino-alpha-L-LNA adenine building blocks is outlined and initial results from thermal denaturation studies are presented.
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Affiliation(s)
- Nicolai K Andersen
- Nucleic Acid Center, Department of Physics and Chemistry, University of Southern Denmark, Odense M, Denmark
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8
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Nielsen P, Shaikh KI, Nielsen LJ, Andersen NK, Spácilová L, Nielsen H, Kocalka P, Christensen MS. Nucleic acid duplexes with zippers of additional nucleobases and aromatics in minor or major groove. Nucleic Acids Symp Ser (Oxf) 2008; 52:5-6. [PMID: 18776225 DOI: 10.1093/nass/nrn003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Two series of thymidine derivatives with additional nucleobases/aromatics attached to either the 5'(S)-C- or the 5-position were prepared by epoxide opening and/or "click chemistry" cycloaddition protocols and introduced into DNA duplexes. Interstrand base-base communication in the minor groove and intrastrand stacking interactions in the major groove were detected.
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Affiliation(s)
- Poul Nielsen
- Nucleic Acid Center, Department of Physics and Chemistry, University of Southern Denmark, 5230 Odense M, Denmark.
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9
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Hrdlicka PJ, Andersen NK, Jepsen JS, Hansen FG, Haselmann KF, Nielsen C, Wengel J. Synthesis and biological evaluation of branched and conformationally restricted analogs of the anticancer compounds 3'-C-ethynyluridine (EUrd) and 3'-C-ethynylcytidine (ECyd). Bioorg Med Chem 2005; 13:2597-621. [PMID: 15755661 DOI: 10.1016/j.bmc.2005.01.029] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2004] [Revised: 01/13/2005] [Accepted: 01/18/2005] [Indexed: 10/25/2022]
Abstract
The synthesis of branched and conformationally restricted analogs of the anticancer nucleosides 3'-C-ethynyluridine (EUrd) and 3'-C-ethynylcytidine (ECyd) is presented. Molecular modeling and (1)H NMR coupling constant analysis revealed that the furanose rings of all analogs except the LNA analog are conformationally biased towards South conformation, and are thus mimicking the structure of ECyd. All target nucleosides were devoid of anti-HIV or anticancer activity.
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Affiliation(s)
- Patrick J Hrdlicka
- Nucleic Acid Center, Department of Chemistry, University of Southern Denmark, DK-5230 Odense M, Denmark
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Harrison AP, Erlwanger KH, Elbrønd VS, Andersen NK, Unmack MA. Gastrointestinal-tract models and techniques for use in safety pharmacology. J Pharmacol Toxicol Methods 2004; 49:187-99. [PMID: 15172015 DOI: 10.1016/j.vascn.2004.02.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2004] [Accepted: 02/20/2004] [Indexed: 12/22/2022]
Abstract
The gastrointestinal tract (GI tract), which extracts nutrients, electrolytes, minerals, and water, is prone to injury as a result of oral drug administration. Clinical assessment of the GI tract is often limited to measurements of transit time and observations of vomiting or diarrhoea, despite the existence of methods and techniques capable of assessing specific changes in GI function at the membrane, cell, and whole animal levels. Membrane studies, record the uptake of solutes, and electrolyte transport, assessing the affects of compounds on transepithelial GI transport and flux. Such methods lend themselves to permeability, immunohistochemistry, morphology, and molecular biology techniques. Isolated cells from the GI tract or cultured cell lines provide knowledge of regulation and function at a cellular level, whilst motility patterns, taken in vivo or from biopsies, provide information at a more integrated level. In anesthetised animals, ligated segments of the intestine can be infused with test compounds, providing information about absorptive and secretory processes important for the treatment of diarrhoea. Computer simulations and modelling are used to predict the disposition of a chemical and its metabolite and can, to some extent, replace animal testing, thereby reducing development costs. Indeed, software programs can be used to simulate the dissolution, absorption, distribution, metabolism, and excretion (ADME) properties of potential drugs in the human GI tract. Finally, advances in the field of imaging, combined with endoscopy, have resulted in a wireless capsule, allowing the inspection of the GI tract anatomy and pathology without surgical intervention. It is concluded that the field of safety pharmacology could rapidly, cheaply, and routinely incorporate membrane, isolated tissue, and endoscopy techniques for GI tract testing of drugs.
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Affiliation(s)
- A P Harrison
- Department of Anatomy and Physiology, The Royal Veterinary and Agricultural University, Grønnegårdsvej 7, DK-1870 Frederiksberg C, Denmark.
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