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Previously posted on my board.
This underscores some of the problems with the long-chain complex structure of synthetic GH and touches on why people in part experience a wide variety of experiences concerning effectiveness and red welts.
Aggregation
Protein molecules can often undergo self-association by physical or chemical forces to form dimers, trimers, tetramers, or higher oligomers. This self-association or aggregation is a common problem during formulation development and pharmaceutical processing. Although aggregation is physical instability, it can lead to loss of biological activity. However, some proteins may exert their biological effects as a dimer, trimer, or higher oligomeric forms and may lose biological activity on dissociation. For instance, tumor necrosis factor exists as a compact trimer in aqueous solutions, and maintenance of its trimeric structure is essential for its activity. In any case, a study of the aggregation phenomena is crucial to developing a successful peptide or protein formulation. Even if aggregation does not result in loss of bioactivity, formation of insoluble aggregates can cause blockage of tubing, membranes, or pumps in an infusion set, as is the case with insulin. Furthermore, because aggregation leads to an increase in effective molecular weight, the aggregated protein may be more immunogenic.
[To be clear here, aggregation may be responsible for the ability of a particular substance, to provoke an immune response... such as is sometimes seen w/ black market GH]
Aggregation behavior of human growth hormone
The hGH can undergo aggregation to form a dimer or higher molecular weight oligomers. Such aggregation can take place during formulation, processing, storage, and reconstitution. Phenolic compounds also induce aggregation of hGH. The most common aggregation product is a stable, noncovalent dimer that is chemically identical to hGH but is essentially inactive in bioassay. Zinc ions (Zn2+) can also induce dimerization of hGH. Two Zn2+ ions associate per dimer of hGH, and the formation of the Zn2+–hGH dimeric complex may be important for the storage of hGH in secretory granules. Replacement of potential Zn2+ ligands such as His18, His21, and Glu174 in hGH with alanine has been reported to weaken Zn2+ binding, thereby preventing formation of hGH dimer. Aggregation of hGH was known to be a problem during its preparation from pituitary gland before the availability of the recombinant protein. A process of ultrafiltration was shown to result in an aggregate-free preparation. Aggregation of hGH can be induced by freezing and thawing or by agitation. Product literature of recombinant hGH from Eli Lilly (Humatrope) instructs to reconstitute the lyophilized powder by injecting the diluent against the glass wall and mixing by gentle swirling, without any shaking. As currently formulated, hGH readily precipitates out of neutral solution with vigorous mixing. Besides stability and bioactivity considerations, any aggregation of hGH may increase the antigenicity of the product.
[To be clear aggregation of GH has the capacity to stimulate the production of antibodies or the capacity to react with an antibody.]
Therapeutic Peptides and Proteins Formulation,
Processing, and Delivery Systems,Second Edition,
Ajay K. Banga, Ph.D.,
CRC Press 2006
Processing, and Delivery Systems,Second Edition,
Ajay K. Banga, Ph.D.,
CRC Press 2006
This underscores some of the problems with the long-chain complex structure of synthetic GH and touches on why people in part experience a wide variety of experiences concerning effectiveness and red welts.
Aggregation
Protein molecules can often undergo self-association by physical or chemical forces to form dimers, trimers, tetramers, or higher oligomers. This self-association or aggregation is a common problem during formulation development and pharmaceutical processing. Although aggregation is physical instability, it can lead to loss of biological activity. However, some proteins may exert their biological effects as a dimer, trimer, or higher oligomeric forms and may lose biological activity on dissociation. For instance, tumor necrosis factor exists as a compact trimer in aqueous solutions, and maintenance of its trimeric structure is essential for its activity. In any case, a study of the aggregation phenomena is crucial to developing a successful peptide or protein formulation. Even if aggregation does not result in loss of bioactivity, formation of insoluble aggregates can cause blockage of tubing, membranes, or pumps in an infusion set, as is the case with insulin. Furthermore, because aggregation leads to an increase in effective molecular weight, the aggregated protein may be more immunogenic.
[To be clear here, aggregation may be responsible for the ability of a particular substance, to provoke an immune response... such as is sometimes seen w/ black market GH]
Aggregation behavior of human growth hormone
The hGH can undergo aggregation to form a dimer or higher molecular weight oligomers. Such aggregation can take place during formulation, processing, storage, and reconstitution. Phenolic compounds also induce aggregation of hGH. The most common aggregation product is a stable, noncovalent dimer that is chemically identical to hGH but is essentially inactive in bioassay. Zinc ions (Zn2+) can also induce dimerization of hGH. Two Zn2+ ions associate per dimer of hGH, and the formation of the Zn2+–hGH dimeric complex may be important for the storage of hGH in secretory granules. Replacement of potential Zn2+ ligands such as His18, His21, and Glu174 in hGH with alanine has been reported to weaken Zn2+ binding, thereby preventing formation of hGH dimer. Aggregation of hGH was known to be a problem during its preparation from pituitary gland before the availability of the recombinant protein. A process of ultrafiltration was shown to result in an aggregate-free preparation. Aggregation of hGH can be induced by freezing and thawing or by agitation. Product literature of recombinant hGH from Eli Lilly (Humatrope) instructs to reconstitute the lyophilized powder by injecting the diluent against the glass wall and mixing by gentle swirling, without any shaking. As currently formulated, hGH readily precipitates out of neutral solution with vigorous mixing. Besides stability and bioactivity considerations, any aggregation of hGH may increase the antigenicity of the product.
[To be clear aggregation of GH has the capacity to stimulate the production of antibodies or the capacity to react with an antibody.]