Unmodified DNA oligonucleotides
 

1. The synthesis scale defines the amount of starting material, it is not the yield of the finalised oligo. Due to the many steps of synthesis, processing and purification the final yield is significantly lower.

2. Oligos are delivery exclusively with purification. At least a cartridge purification is applied. We do not offer unpurified oligo nor only desalted oligos. By default all oligonucleotides with more than 60 bases in standard scales S - L are purified by HPLC (optional PAGE may be chosen).

3. The yields provided at "guaranteed delivery amount" are valid for a mixed 20mer DNA-sequence. For significantly shorter or longer oligos as well as for homopolymers this yield may differ. According to our experience, the actual delivery amounts exceed the guaranteed yields significantly, certainly we deliver the total yield.

4. Routinely, each oligo up to a length of 50 bases will be checked for quality by Maldi mass spectrometry.

• Non-modified oligonucleotides between 140 and 200 bases
• Optimised synthesis conditions due to special cycles and chemicals
• Continuous monitoring of synthesis progress (trityl monitoring)
• Guaranteed yield > 250 pmol of purified oligonucleotide
• Inclusive 2-step purification: Reverse phase HPLC purification is followed by PAGE purification

How many correct clones can be expected ? We have analysed the results for you:

In cooperation with the University of Ulm, we exemplarily analysed a 200mer synthesised by biomers.net, which was amplified by PCR, cloned and finally sequenced. Out of 10 analysed clones 30% showed exactly the designated sequence. In a further clone a one base-insertion was found at position 22, in another the deletion of one base at position 147. In four additional clones several deletions were found. Due to synthesis errors, we expected mainly deletions of one or two bases, transitions and transversions as well as insertions. Interestingly, besides these expected changes, we found several deletions between 4 and 16 bases in a row. These can hardly be explained by synthesis errors, because the cyclic reaction of the synthesis is very unlikely to "skip" more than one or two bases. Likely the reason for these deletions is connected to the PCR reaction or the polymerase used (see also Hecker et al., 1998, BioTechniques 24:256-260).

In further analyses an average of 3 correct clones out of 5 has been found.