Glutamic acid valine and lysine

[zeevee]

Some background pathology before I ask my question :
glutamic acid is an acid /negatively charged.Its replaced by neutral valine in sickle cell disease >> resultantly Hb becomes less negatively charged and moves towards the cathode (-) in electrophoresis .

Now if glutamic acid is replaced by lysine ( which is basic) it becomes more positively charged and moves towards the cathode even more .

My question is : H ions ( acid ) are positively charged while OH- ( aka base) are negatively charged so how can glutamic ACID be negatively charged to begin with ?

Why are acidic amino acids negatively charged ?

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[chillaxbro]

Glutamic acid can be negatively charged if it gives off it's proton ie in an alkaline solution. Read about henderson hasselbach equation and pKa

 

[Kazaki]

An acid dissociates into a proton and its conjugate base. Proton is positive, conjugate base is negative.