:6-Methylisoxanthopterin

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| ImageFile = 6-Methylisoxanthopterin Structural Formula V.1.svg

| ImageSize = 200px

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| IUPACName = 2-Amino-6-methyl-1,8-dihydropteridine-4,7-dione

| OtherNames = 6-MI; 6MI

| Section1 = {{Chembox Identifiers

| CASNo = 712-38-9

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = ZFA4TQK4XW

| PubChem = 345267

| ChemSpiderID = 306197

| SMILES = CC1=NC2=C(NC1=O)NC(=NC2=O)N

| InChI=1S/C7H7N5O2/c1-2-5(13)10-4-3(9-2)6(14)12-7(8)11-4/h1H3,(H4,8,10,11,12,13,14)

| InChIKey = DYXQYFTUVSIKIG-UHFFFAOYSA-N

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| Section2 = {{Chembox Properties

| C=7|H=7|N=5|O=2

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| Section3 = {{Chembox Hazards

| MainHazards =

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6-Methylisoxanthopterin (6MI) is a base analog for the nucleotide guanine. It is useful as a fluorescent indicator because unlike most other base analogs, quenching does not occur when it is incorporated into a double helix. In fact, it exhibits a 3 to 4-fold increase in quantum yield when it is incorporated into a duplex formation.{{cite journal|doi=10.1021/acs.jpcb.6b07369|last=Moreno|first=Andrew|title=Photophysical Characterization of Enhanced 6-Methylisoxanthopterin Fluorescence in Duplex DNA|journal=The Journal of Physical Chemistry B|volume=120|issue=48|pages=12232–12248|year=2016|pmid=27934220}} This allows 6MI to be used to probe the dynamics of DNA or RNA helices using a technique such as fluorescence polarization anisotropy. {{cite journal|doi=10.1021/ja902797j|pmid=19537712|title=Probing the Dynamics of the P1 Helix within the Tetrahymena Group I Intron|journal=Journal of the American Chemical Society|volume=131|issue=27|pages=9571–9578|last=Shi|first=Xuesong|pmc=2758093|year=2009}}