Lyophilized (freeze dried) proteins are considerably more stable than proteins in solution, consequently many proteins ship in lyophilized forms. This extends the time and temperature range at which the proteins can be shipped while maintaining the activity of the protein – good for the environment and your experiments. Lyophilized proteins are generally stable at room temperature for one month (we verify stability over a standard 3-day shipping cycle), or frozen at -20 ^oC or -80 ^oC for 2 years. However, on occasion lyophilization can cause partial loss of activity and damage protein structure, so some proteins are supplied in buffer.