Complex sentence: The proteins applied in the first dimension will move along the gel and will accumulate at their isoelectric point; that is, the point at which the overall charge on the protein is 0 (a neutral charge).
Split into simpler sentences: The proteins applied in the first dimension will move along the gel and will accumulate at their isoelectric point. That is, the point at which the overall charge on the protein is 0 (i.e a neutral charge).