The present invention provides a method for preparing a sample characterized by binding a substance A containing a hydrazide group to a sugar chain and/or a sugar derivative via hydrazone formation between the hydrazide group of the substance A and the reducing end of the sugar chain and/or the sugar derivative thereby to enable the separation and purification of the sugar chain and/or the sugar derivative for an analytical sample from a biological sample containing the sugar chain and/or the sugar derivative by a simple operation.
Provided are dyes and compositions which are useful in a number of applications, such as the detection and monitoring protein aggregation, kinetic studies of protein aggregation, neurofibrillary plaques analysis, evaluation of protein formulation stability, and analysis of molecular chaperone activity.