Thepresynapticproteina-synuclein(aSyn)isan‘intrinsicallydisorderedprotein’thatishighlydynamicinconformation.TransientintramolecularinteractionsbetweenitschargedNandCtermini,andbetweenitshydrophobicregionandtheCterminus,preventself-association.Theseinteractionsinhibittheformationofinsolubleinclusions,whicharethepathologicalhallmarkofParkinson’sdiseaseandmanyothersynucleinopathies.ThisreviewdiscusseshowtheseintramolecularinteractionsareinfluencedbythespecificenvironmentaSynisin.Wediscusshowcharge,pH,calcium,andsaltaffectthephysiologicalstructureofmonomericaSyn,andhowtheymayfavourtheformationoftoxicstructures.ThemoreweunderstandthedynamicconformationsofaSyn,thebetterwecandesigndesperatelyneededtherapeuticstopreventdiseaseprogression.