Isopropyl- β - D -thiogalactopyranoside
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| General | |||||||||||||||||||
| Surname | Isopropyl- β - D -thiogalactopyranoside | ||||||||||||||||||
| other names |
IPTG |
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| Molecular formula | C 9 H 18 O 5 S | ||||||||||||||||||
| Brief description |
colorless and odorless powder |
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| properties | |||||||||||||||||||
| Molar mass | 238.302 g mol −1 | ||||||||||||||||||
| Physical state |
firmly |
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| Melting point |
110-112 ° C |
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| solubility |
soluble in water (10 g l −1 at 20 ° C) |
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | |||||||||||||||||||
Isopropyl β - D -thiogalactopyranoside ( IPTG ) is a galactose - thioglycoside ( S glycoside) which as an artificial inducer of the lactose operon in Escherichia coli is used.
Chemical and physical properties
The rotation value α is −28.6 ° (589 nm; 20 ° C; 0.82 g / 100 ml H 2 O).
Biological properties
IPTG acts as an activator (inductor) of the lac operon by binding to the lac repressor (the protein product of the lacI gene). This one takes place allosteric conformational change of the repressor that its interaction with the lac - Operators inhibited. In contrast to lactose or allolactose, IPTG is not converted by bacteria in the natural metabolism , so its concentration is constant during an experiment and the repressor remains inactivated. Such non-metabolized inducers are called "gratuitous inducers" in the English technical language, in German less descriptively and not entirely accurately called "artificial inductors". Some IPTG preparations can contain carcinogenic contaminants.
use
IPTG is in the molecular biology used to recombinant proteins by expression of cloned genes to produce. The desired gene is under the control of a promoter regulated by lac repressor . Such a promoter-gene fusion is usually located on a plasmid that is used to transform bacteria . So that the gene is initially switched off and only converted into protein in a controlled manner by adding IPTG ( transcription and translation ), the cells must express Lac repressor in sufficient quantities. Furthermore, it is often (and mostly unnecessarily) used in the blue-white selection . The multicopy plasmids used in this selection usually carry lac operators and thus titrate the few cellular lac repressor molecules.
literature
- Joseph Sambrook , David W. Russell: Molecular cloning. A laboratory manual. 3rd edition. Cold Spring Harbor Laboratory Press, Cold Spring Harbor NY 2001, ISBN 0-87969-577-3 .
- Robert Schleif: Genetics and Molecular Biology. 2nd edition. The Johns Hopkins University Press, Baltimore et al. 1993, ISBN 0-8018-4673-0 .
Individual evidence
- ↑ a b c data sheet isopropyl-β-D-thiogalactopyranoside (PDF) from Carl Roth , accessed on July 12, 2018.
- ↑ a b data sheet IPTG at Sigma-Aldrich , accessed on February 2, 2019 ( PDF ).
- ↑ Manfred Eichhorn: German Dictionary of Biology , 1999, Routledge Chapman & Hall.
- ↑ ECHA : Summary of Classification and Labeling: IPTG .
- ↑ RM Cranenburgh, KS Lewis & JA Hanak (2004): Effect of plasmid copy number and lac operator sequence on antibiotic-free plasmid selection by operator-repressor titration in Escherichia coli. In: J Mol Microbiol Biotechnol. Vol. 7, pp. 197-203. PMID 15383717 .