This product should be soluble at 1 mg/mL in TE buffer.
If you are still having issue dissolving the product, please contact our Technical Service team who can assist you with further troubleshooting and/or investigation. We kindly ask you to navigate to the link https://www.sigmaaldrich.com/techservice, click on "Report Product Issues" under the Products Section with all the required information so that a member of our team can reach out to you to assist further. Thank you.