to check dat group is basic i use to see lone pair negative charge but in lysine how is NH2 AND O- BASIC also tell how to identify acidic group in good struc

Dear student,

Basic amino acids are polar and positively charged at pH values below their pK_a's, and are very hydrophilic. Even though the basic amino acids are almost always in contact with the solvent, the side chain of lysine has a marked hydrocarbon character, so it is often found NEAR the surface, with the amino group of the side chain in contact with solvent. Note that in the drawing, histidine is shown in the protonated form, while at pH 7.0, the imidazole would exist predominantly in the neutral form.

your  concept is right ...

to identify acidic group always see weather the group is multiple bonded or not...

some of the acidic groups are  N⁺(CH₃)₃ , NO₂ , C00H , CH0,CN  all these are bonded by a multiple

bond, in CN there is C-N triplebond

        in CH0 there is C-O double bond

if group posses lone pairs with -ve charge then always basic & if group posses

+ve charge or multiple bond then it is acidic...