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- Jul 25, 2008
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- 1,700
xxx said:
Yes that is normal.
What happens is equal amounts of peptide by weight are deposited in a vial via machine. The vial is partially stoppered and transported inside the lyophilizer. The contents of the vial are exposed to the nitrogen flush and air turbulence is created. The peptides may settle in different patterns. Vials are stoppered fully in the lyophilizer. The components of the freezing cycle can vary from vial to vial very easily. The rate and manner of a freeze cycle can effect the physical form of the substance being frozen. For example if the freezing is slightly slower it can lead to formation of large ice crystals and tight very dense compaction of the peptide. Adhesion to the sides of vials can happen when water vapor escapes during a process where it goes from a solid to a gas without ever going through a liquid phase.
The product temperature, the condenser temperature, chamber pressure, condenser pressure all may vary minutely between vials and account for the visual difference of the freeze-dried product between vials.
All of these cycle parameters, the shelf freeze temperature, the product freeze temperature, the freezing "soak" time, the primary drying shelf temperature, cabinet pressure, product temperature for establishment of fill vacuum, secondary shelf drying temperature, and secondary drying time all may contribute to visually different appearance of vial contents if they very even slightly between vials.
Circulating thermal fluid may influence any vacuum chamber leakage. Vapors migrating back from the vacuum pumping system may also impact pressure... these things again may contribute to a different appearance between vials.
The difference in appearance can be dramatic from very light and fluffy volumized to tight and compact crystals to a single solid to a sprayed inside the vial appearance. Sometimes when you are dealing with small amounts such as 1 or 2mgs it may not appear that there is much content in the vial.
However the machinery that deposits the initial peptide or compound into the vial always does its job accurately and the identical peptide/compound weight will be found in all vials without regard to visual appearance.
Now the smaller the peptide the more likely that the appearance will be fairly uniform across all vials in a batch. For instance a GHRP is just a few amino acids long with little 3-dimensional aspect to its structure. Freeze drying "flattens" the 3-dimensional structure. It is more likely that this flattening will be fairly similar between each peptide chain in the vial and across all vials. Thus less opportunity for the afore-mentioned freeze cycle variables to have a big impact.
However longer more complex structures such as GRF(1-29) or IGF-1 LR3 especially are far more prone to have variable "flattening" between peptides in the vials. There is more opportunity for the variability in the freeze cycle components to have an impact. That is why you may see IGF-1 sprayed in the vial, or fluffy, or crystallized in tiny balls or globbed into big balls or volumized or so super dense it doesn't appear to be much present.
This is all normal. Whenever I see people post pictures of vials with different appearances feeling that they are sometimes ripped off I sometimes smile. They are use to shopping for Cheerios not freeze-dried peptides.
The important part is to have the peptide fully re-dimesionalize upon reconstitution. In other words rehydrating returns all freeze-dried peptides in the vial no matter what they look like to their initial and bio-active 3-dimensional shape.
I hope this helps. I am going to post this on the open forum.
Later.
-Dat
