MTSL

{{Chembox | Watchedfields = changed | verifiedrevid = 405925388 | ImageFile = MTSL chemical structure.png | ImageSize = 150px | PIN = {2,2,5,5-Tetramethyl-3-[(2-methyl-2,2-dioxo-2λ⁶-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 that is used as a nitroxide 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, consisting of the nitroxide and the thiosulfonate ester functional groups. 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 (CH₃SO₂⁻) is the leaving group: :RSO₂S-''nitroxide'' + ''protein''-SH → ''protein''-S-S-''nitroxide'' + RSO₂H The heterodisulfide bond to the 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 to the mass of the protein or peptide to which it is attached. The cysteine can be introduced using site-directed mutagenesis, and hence most positions in a protein can be labelled.

==Spectroscopy== In Nuclear magnetic resonance the introduction of the paramagnetic group increases the relaxation rate of nearby nuclei.<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 (2.5 nm) as opposed to about 6 Å (0.6&nbsp;nm) using the nuclear Overhauser effect. Spin labelling with MTSL is frequently used in investigation of residual structure in intrinsically unstructured proteins.

== References == <references/>

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