# MTSL

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/MTSL
> Markdown URL: https://mediated.wiki/source/MTSL.md
> Source: https://en.wikipedia.org/wiki/MTSL
> Source revision: 1118575112
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

{{Chembox
| Watchedfields = changed
| verifiedrevid = 405925388
| ImageFile = MTSL chemical structure.png
| ImageSize = 150px
| PIN = {2,2,5,5-Tetramethyl-3-[(2-methyl-2,2-dioxo-2λ<sup>6</sup>-disulfan-1-yl)methyl]-2,5-dihydro-1''H''-pyrrol-1-yl}oxyl
| OtherNames = MTSL
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 117873
| InChI = 1/C10H18NO3S2/c1-9(2)6-8(7-15-16(5,13)14)10(3,4)11(9)12/h6H,7H2,1-5H3
| InChIKey = BLSCGBLQCTWVPO-UHFFFAOYAW
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C10H18NO3S2/c1-9(2)6-8(7-15-16(5,13)14)10(3,4)11(9)12/h6H,7H2,1-5H3
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = BLSCGBLQCTWVPO-UHFFFAOYSA-N
| CASNo_Ref = {{cascite|correct|??}}
| CASNo = 81213-52-7
| PubChem = 133628
| SMILES = CC1(C=C(C(N1[O])(C)C)CSS(=O)(=O)C)C
}}
|Section2={{Chembox Properties
| C=10 | H=18 | N=1 | O=3 | S=2
| Appearance = 
| Density = 
| MeltingPt = 
| BoilingPt = 
| Solubility = }}
|Section3={{Chembox Hazards
| MainHazards = 
| FlashPt = 
| AutoignitionPt = }}
}}

'''MTSL''' (''S''-(1-oxyl-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrol-3-yl)methyl methanesulfonothioate) is an [organosulfur compound](/source/organosulfur_compound) that is used as a [nitroxide](/source/nitroxide)  [spin label](/source/spin_label).<ref name= Altenbach>Christian Altenbach, Kyoung-Joon Oh, René J. Trabanino, Kálmán Hideg, Wayne L. Hubbell "Estimation of Inter-Residue Distances in Spin Labeled Proteins at Physiological Temperatures:  Experimental Strategies and Practical Limitations" Biochemistry, 2001, volume 40, pp 15471–15482. {{doi|10.1021/bi011544w}}</ref>  MTSL is [bifunctional](/source/bifunctional), consisting of the nitroxide and the thiosulfonate ester [functional group](/source/functional_group)s.  The nitroxide label is sterically protected, so it is relatively unreactive.

==Labeling==
MTSL is attached to proteins by reaction with thiol groups. The reaction exploits standard reactivity of thiosulfate esters. [Methanesulfinate](/source/Sulfinic_acid) (CH<sub>3</sub>SO<sub>2</sub><sup>−</sup>) is the leaving group:
:RSO<sub>2</sub>S-''nitroxide''  +  ''protein''-SH  →  ''protein''-S-S-''nitroxide''  +  RSO<sub>2</sub>H
The [heterodisulfide](/source/heterodisulfide) bond to the [cysteine](/source/cysteine) residue is robust, enabling site-directed spin labelling.<ref>Kenyon, G.L. and Bruice, T.W. (1977). Novel sulfhydryl reagents. Methods In Enzymology 47, 407-430. {{doi|10.1016/0076-6879(77)47042-3}}</ref><ref>Berliner, L.J., Grunwald, J., Hankovszky, H.O., Hideg, K. (1982). A novel reversible thiol-specific spin label: papain active site labeling and inhibition. Analytical Biochemistry 119, 450-455. {{doi|10.1016/0003-2697(82)90612-1}}</ref> The MTSL moiety will add 184.3 [daltons](/source/atomic_mass_unit) to the mass of the [protein](/source/protein) or [peptide](/source/peptide) to which it is attached. The cysteine can be introduced using [site-directed mutagenesis](/source/site-directed_mutagenesis), and hence most positions in a protein can be labelled.

==Spectroscopy==
In [Nuclear magnetic resonance](/source/Nuclear_magnetic_resonance) the introduction of the paramagnetic group increases the relaxation rate of nearby [nuclei](/source/atomic_nucleus).<ref name= Altenbach/> Its presence can be detected as peak broadening and loss of intensity in peaks corresponding to nearby nuclei. Hence proximity can be inferred for all nuclei, that are affected. A major advantage of this method over traditional methods for obtaining distance restraints in protein NMR is the increased length, as paramagnetic relaxation enhancement can detect distances up to 25 [Å](/source/Angstrom) (2.5 [nm](/source/nanometer)) as opposed to about 6 Å (0.6&nbsp;nm) using the [nuclear Overhauser effect](/source/nuclear_Overhauser_effect). Spin labelling with MTSL is frequently used in investigation of residual structure in [intrinsically unstructured proteins](/source/intrinsically_unstructured_proteins).

== References ==
<references/>

{{DEFAULTSORT:Mtsl}}
Category:Pyrrolines
Category:Amine oxides

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Adapted from the Wikipedia article [MTSL](https://en.wikipedia.org/wiki/MTSL) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/MTSL?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.