I've been transforming E. coli via heat shock in order to insert oligonucleotides (around 50 nt); however, none of my experiments have given positive results so far. I begin to question the efficiency of chemical transformation, especially for short DNA fragments. Is there such a notable difference between chemical and electro transformation?
EDIT: I'm checking for CRISPR array expansion, so my oligos have a protospacer length and structure. I'm using BL21(DE3) cells which have an IPTG-inducible T7 that I'm first transforming with a Cas1-Cas2 plasmid. Then, I induce the cells in order to express those proteins, make them competent, and transform then once again but with the oligos and an eGFP plasmid (for some sort of selection). To check for positive results, I'm amplifying the leader-repeat junction of the CRISPR array and compare its length (via electrophoresis) with a usual array that has no integrands.