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Biomedical subjects

B H Frank

Publications and source records attributed to B H Frank.

At least 19 recordsLinked to original sources
PubMed2001

Insulin self-association and the relationship to pharmacokinetics and pharmacodynamics.

The treatment of type 1 diabetes requires multiple, daily injections of insulin. While many improvements involving formulation adjustments have been made in an attempt to optimize therapy, clinical experience indicates that the commercially available insulin preparations used for treatment have significant limitations. One principal deficiency relates to poor simulation of the physiological insulin secretion pattern, making achieving normalization of blood glucose concentrations difficult. Endogenous insulin secretion in nondiabetic subjects is characterized by a pulsatile profile that displays multiple, meal-stimulated phases and low basal concentrations between meals and overnight. Optimal diabetes therapy, therefore, requires insulin preparations that display a rapid onset of action with corresponding rapid clearance to provide for meal ingestion as well as preparations that can maintain a sustained, peakless profile for basal requirements. Recent efforts in pharmaceutical research have used the concept of rational-based design of the insulin molecule in an attempt to produce preparations that display more ideal pharmacological profiles. Using detailed structural information obtained from X-ray crystallographic studies to guide design strategies and exploit the nonrestrictive synthetic capabilities of recombinant DNA technology, researchers have prepared a number of insulin analogs that display a reduced propensity towards self-association. Clinical evaluations have shown that these so called "monomeric" analogs better mimic the meal-stimulated pharmacokinetics of insulin secretion observed in nondiabetics. Two monomeric insulin analog preparations have successfully obtained regulatory approval and are now commercially available. Efforts to produce optimized basal-acting insulin analogs have lagged behind. While some of these analogs have been engineered using recombinant DNA technology, design strategies in many cases exploit physicochemical properties of insulin other than self-association. One basal insulin analog has recently received regulatory approval. This paper reviews insulin self-association and its relationship to pharmacokinetics and pharmacodynamics. Particular emphasis is placed on the approaches used to manipulate self-assembly resulting in meal-time insulin analogs that display optimal pharmacological properties. Other design strategies used to develop improved basal insulin preparations are also considered.

Diabetes Mellitus, Type 1↗
PubMed2000

Structural studies of a crystalline insulin analog complex with protamine by atomic force microscopy.

Crystallographic studies of insulin-protamine complexes, such as neutral protamine Hagedorn (NPH) insulin, have been hampered by high crystal solvent content, small crystal dimensions, and extensive disorder in the protamine molecules. We report herein in situ tapping mode atomic force microscopy (TMAFM) studies of crystalline neutral protamine Lys(B28)Pro(B29) (NPL), a complex of Lys(B28)Pro(B29) insulin, in which the C-terminal prolyl and lysyl residues of human insulin are inverted, and protamine that is used as an intermediate time-action therapy for treating insulin-dependent diabetes. Tapping mode AFM performed at 6 degrees C on bipyramidally tipped tetragonal rod-shaped NPL crystals revealed large micron-sized islands separated by 44-A tall steps. Lattice images obtained by in situ TMAFM phase and height imaging on these islands were consistent with the arrangement of individual insulin-protamine complexes on the P4(1)2(1)2 (110) crystal plane of NPH, based on a low-resolution x-ray diffraction structure of NPH, arguing that the NPH and NPL insulins are isostructural. Superposition of the height and phase images indicated that tip-sample adhesion was larger in the interstices between NPL complexes in the (110) crystal plane than over the individual complexes. These results demonstrate the utility of low-temperature TMAFM height and phase imaging for the structural characterization of biomolecular complexes.

Crystallization↗
PubMed2000

Stability of U-10 and U-50 dilutions of insulin lispro.

BACKGROUND: Insulin lispro, a rapid acting analog of human insulin, has been shown to be useful in the treatment of children with diabetes. However, lower concentrations of this insulin may be needed to facilitate optimal clinical use. Therefore, the stability of insulin lispro when diluted with an appropriate diluent was evaluated. METHODS: Insulin lispro (U-100, 100 U/mL) was diluted with sterile Neutral Protamine Hagedorn (NPH) diluent to U-10 and U-50. After storage for 7, 14, 21, 28, and 32 days at 5 degrees C and 30 degrees C, the diluted insulins were analyzed by high-performance liquid chromatography (HPLC) to determine potency, purity, polymer, and preservative (metacresol or phenol) content in addition to physical appearance and pH determinations. Microbiological testing for preservative effectiveness was performed on the U-10 and U-50 solutions after 32 days at both temperatures. RESULTS: U-10 and U-50 dilutions of insulin lispro stored at 5 degrees C and 30 degrees C maintained potency and purity throughout the 32-day testing period. Additionally, both control and diluted vials maintained antimicrobial effectiveness. CONCLUSION: Insulin lispro when diluted with the appropriate diluent demonstrates acceptable stability when stored at 5 degrees C and 30 degrees C for a period of 32 days.

Chemical Phenomena↗
PubMed1999

Differences in the cellular processing of AspB10 human insulin compared with human insulin and LysB28ProB29 human insulin.

Cellular metabolism studies were performed comparing human insulin with two rapid-acting analogs, LysB28ProB29 insulin (LysPro) and AspB10 insulin (B10-Asp). B10-Asp bound to isolated hepatocytes at 37 degrees C to a greater extent than LysPro or native insulin, which were equivalent. The rate of degradation was similar for the three materials, resulting in a significant reduction in the degraded/bound ratio for the B10 analog. The processing of membrane-bound material was examined by incubating cells with hormone at 4 degrees C, removing unbound insulin, and incubating the cells at 37 degrees C. Again, binding was greater for B10-Asp versus LysPro or native insulin, with a reduction in the degraded/bound ratio. Hormone internalization and processing was examined by an acid wash of cells incubated with 125I(A14)-labeled hormone to remove surface-bound materials. The processing rate was slower for B10-Asp versus LysPro or native insulin. Cell extraction and examination on molecular-sieve chromatography confirmed that B10-Asp was processed at a slower rate than either LysPro or native insulin. Intact B10-Asp was found in the cell after 4 hours, whereas all native insulin and LysPro were degraded by 90 to 120 minutes. B10-Asp also caused a greater incorporation of thymidine into DNA in cultured cells than LysPro or native insulin, which were similar. These data show that the cellular processing of LysPro is essentially identical to that of native insulin. However, B10-Asp has markedly different properties and is processed much more slowly. The prolonged cell residence time of B10-Asp could contribute to its greater effects on cell growth and mitogenesis.

Animals↗
PubMed1999

A novel protein cross-linking reaction in stressed Neutral Protamine Hagedorn formulations of insulin.

The covalent insulin-protamine product molecules formed by heat stress in Neutral Protamine Hagedorn formulations of insulin and the insulin analogue [LysB28,ProB29] were examined by mass spectrometry. The results demonstrated that the covalent cross-link between insulin and protamine was not caused by linkage through the protamine N-terminal amino group, as had been previously thought. Our results indicate that the linkage was formed between the side chain of a protamine arginine and a histidine in the insulin B chain, resulting in a net mass change of -5 Da, compared to the sum of the protamine and insulin molecular masses. A mechanism for this new type of covalent cross-linking reaction is proposed.

Chemistry, Pharmaceutical↗
PubMed1999

Preparation of a microcrystalline suspension formulation of Lys(B28)Pro(B29)-human insulin with ultralente properties.

The monomeric analogue, Lys(B28)Pro(B29)-human insulin (LysPro), has been crystallized using similar conditions employed to prepare extended-acting insulin ultralente formulations. In the presence of zinc ions, sodium acetate and sodium chloride, but without phenolic preservative, LysPro surprisingly forms small rhombohedral crystals with similar morphology to human insulin ultralente crystals with a mean particle size of 20 +/- 1 microm. X-ray powder diffraction studies on the LysPro crystals prior to dilution in ultralente vehicle ([NaCl] = 1.2 M) revealed the presence of T(3)R(3)(f) hexamers. Consistent with human insulin ultralente preparations, LysPro crystals formulated as an ultralente suspension ([NaCl] = 0. 12 M) contain T(6) hexamers indicating that a conformational change occurs in the hexamer units of the crystals upon dilution of the salt concentration. The pharmacological properties of subcutaneously administered ultralente LysPro (ULP) were compared to ultralente human insulin (UHI) using a conscious dog model (n = 5) with glucose levels clamped at basal. There were no statistically significant differences between the kinetic and dynamic responses of ULP compared to UHI [C(max) (ng/mL): 3.58 +/- 0.76, ULP and 3.61 +/- 0. 66, UHI; T(max) (min): 226 +/- 30, ULP and 185 +/- 42, UHI; R(max) (mg/kg min): 11.2 +/- 1.9, ULP and 13.3 +/- 2.0, UHI; and T(Rmax) (min): 336 +/- 11, ULP and 285 +/- 57, UHI]. Although the Pro to Lys sequence inversion destabilizes insulin self-assembly and greatly alters the time action of soluble LysPro preparations, this modification has now been found neither to prevent the formation of ultralente crystals in the absence of phenolics nor to compromise the protracted activity of the insulin analogue suspension.

Animals↗
PubMed1998

Structural and morphological characterization of ultralente insulin crystals by atomic force microscopy: evidence of hydrophobically driven assembly.

Although x-ray crystal structures exist for many forms of insulin, the hormone involved in glucose metabolism and used in the treatment of diabetes, x-ray structural characterization of therapeutically important long-acting crystalline ultralente insulin forms has been elusive because of small crystal size and poor diffraction characteristics. We describe tapping-mode atomic force microscopy (TMAFM) studies, performed directly in crystallization liquor, of ultralente crystals prepared from bovine, human, and porcine insulins. Lattice images obtained from direct imaging of crystal planes are consistent with R3 space group symmetry for each insulin type, but the morphology of the human and porcine crystals observed by AFM differs substantially from that of the bovine insulin crystals. Human and porcine ultralente crystals exhibited large, molecularly flat (001) faces consisting of hexagonal arrays of close packed hexamers. In contrast, bovine ultralente crystals predominantly exhibited faces with cylindrical features assignable to close-packed stacks of insulin hexamers laying in-plane, consistent with the packing motif of the (010) and (011) planes. This behavior is attributed to a twofold increase in the hydrophobic character of the upper and lower surfaces of the donut-shaped insulin hexamer in bovine insulin compared to its human and porcine counterparts that results from minor sequence differences between these insulins. The increased hydrophobicity of these surfaces can promote hexamer-hexamer stacking in precrystalline aggregates or enhance attachment of single hexamers along the c axis at the crystal surface during crystal growth. Both events lead to enhanced growth of ¿hk0¿ planes instead of (001). The insulin hexamers on the (010) and (110) faces are exposed "edge-on" to the aqueous medium, such that solvent access to the center of the hexamer and to solvent channels is reduced compared to the (001) surface, consistent with the slower dissolution and reputed unique basal activity of bovine ultralente insulin. These observations demonstrate that subtle variations in amino acid sequence can dramatically affect the interfacial structure of crystalline proteins.

Animals↗
PubMed1998

Preparation and characterization of a cocrystalline suspension of [LysB28,ProB29]-human insulin analogue.

Soluble preparations of [LysB28,ProB29]-human insulin analogue (LysPro) exhibit more rapid absorption than human insulin upon subcutaneous injection. Biphasic mixtures of LysPro and intermediate-acting insulin suspensions could provide advantages over current preparations for the treatment of diabetes. To prepare biphasic mixtures of LysPro, a suspension formulation of the analogue is required. We have devised a method for crystallizing LysPro with the basic peptide protamine yielding neutral protamine LysPro (NPL) suspension. The crystallization conditions are strongly dependent on the precipitation procedure and temperature. Using various techniques, the crystalline and suspension characteristics of NPL are found to be similar to human insulin (neutral protamine Hagedorn, NPH) (8:1 molar ratio insulin:protamine, rod-shaped crystals, particle size of 4.0-6.0 microns, and Point of Zero Charge at 6.0-7.0). Using a dog model with NPL or NPH injected subcutaneously and glucose levels clamped at basal, NPL was found to have kinetic and dynamic responses analogous to human insulin NPH [Cmax (maximal insulin or LysPro concentration, ng/mL) of 2.61 +/- 0.22, NPL; 2.58 +/- 0.36, NPH, attained at Tmax (min) of 93 +/- 22, NPL; 145 +/- 33 NPH, and Rmax (maximal rate of glucose infusion, mg/kg min) of 10.8 +/- 1.2, NPL; 13.2 +/- 1.9, NPH, attained at TRmax (min) of 277 +/- 58, NPL; 265 +/- 38, NPH]. There are no statistically significant differences between the insulin curves or the glucose responses. These results provide insight into the mechanism of action of NPH suspensions and the relationship to duration of action. Furthermore, the formulation of a suspension of LysPro having an intermediate time-action makes possible the preparation of stable biphasic mixtures containing LysPro and NPL.

Analysis of Variance↗
PubMed1998

Physical stress testing of insulin suspensions and solutions.

Insulin pen-cartridge devices have evolved in order to increase patient compliance and convenience of use in a portable, multiple dosage device. With the advent of a portable insulin containing device, stability considerations have evolved from standard chemical indicators to include the effects of temperature and agitation on physical characteristics. To address these issues, two automated physical stress tests were developed based on market research data and input from regulatory authorities to understand the effect of thermomechanical stress on the product. First, the temperature cycling and resuspension test (TCRT) includes temperature cycling (25-37 degreesC) combined with agitation. The high temperature and extreme agitation test (HTEAT) includes continuous high temperature (37 degreesC) exposure combined with 4 h daily agitation. The total stress exposure is a function of the temperature, agitation, and time. The tests range from moderate stress (TCRT) to considerable stress (HTEAT) determined from the number of cartridge inversions and average daily temperature. Physical stress testing of both insulin suspensions and solution formulations in cartridges were performed and interpreted with respect to multiple endpoints. For suspensions, prolonged exposure to extreme stress caused the protein to form agglomerates, either in the suspension or adhered to the cartridge walls. In contrast, protein solutions subjected to the same extreme stress conditions did not exhibit any visually detectable change. Visual changes in the product under physical stress conditions can increase dose-potency result variability as well as exhibit acid-insoluble aggregates.

Drug Stability↗
PubMed1998

Self-association properties of monomeric insulin analogs under formulation conditions.

PURPOSE: The purpose of the current study was to investigate the effects of two important excipients, zinc and m-cresol, on the self-association properties of a series of monomeric insulin analogs. In this way, the effects on formulation behavior of individual amino acid substitutions in the C-terminal region of the insulin B-chain could be compared. METHODS: The self-association of ten insulin analogs was monitored by equilibrium and velocity analytical ultracentrifugation under three different conditions: (i) in neutral buffer alone; (ii) in neutral buffer containing zinc ion; and (iii) in neutral buffer containing both zinc ion and phenolic preservative (a typical condition for insulin formulations). The self-association properties of these analogs were compared to those of human insulin and the rapid-acting insulin analog Lys(B28)Pro(B29)-human insulin. RESULTS: The analogs in the current study exhibited a wide range of association properties when examined in neutral buffer alone or in neutral buffer containing zinc ion. However, all of these analogs had association properties similar to human insulin in the presence of both zinc and m-cresol. Under these formulation conditions each analog had an apparent sedimentation coefficient of s* = 2.9-3.1 S, which corresponds to the insulin hexamer. CONCLUSIONS: Analogs with changes in the B27-B29 region of human insulin form soluble hexamers in the presence of both zinc and m-cresol, and m-cresol binding overrides the otherwise destabilizing effects of these mutations on self assembly.

Amino Acid Sequence↗
PubMed1998

Highly specific radioimmunoassay for human insulin based on immune exclusion of all insulin precursors.

We describe a rapid and simple insulin RIA in which proinsulin and conversion intermediates do not interfere. Three monoclonal antibodies (S1, S2, and S53) were selected for their specificity (directed, respectively, against the B10 region, the junction between A chain and C-peptide, and the junction between B chain and C-peptide), their affinity constant (approximately 10(10) L/mol), and their interactive properties in mixture. S2 and S53 were able to bind simultaneously to the same proinsulin molecule, whereas neither could bind simultaneously with S1. Preincubation of serum samples with an excess of S2 resulted in capture of proinsulin and conversion intermediates modified at the junction between B chain and C-peptide into immune complexes that no longer reacted with S1. Similarly, preincubation with S53 prevented proinsulin and conversion intermediates modified at the junction between A chain and C-peptide from reacting with S1. Preincubation with an excess of both S2 and S53 left insulin as the sole reactant with S1. Thus, separation of insulin precursors from insulin by mutually exclusive antibodies is feasible, and on the basis of this new principle, a highly specific RIA for insulin was designed. The detection limit was 11 pmol/L, and the inter- and intraassay coefficients of variation were 11% and 5%, respectively. The potential of the assay for use in clinical studies was verified by application to serum samples from control subjects and patients with diabetes or insulinoma.

Animals↗
PubMed1998

First direct assay for intact human proinsulin.

We describe a sensitive two-site sandwich enzyme-linked immunosorbent assay for the measurement of intact human proinsulin in 100 microL of serum or plasma. The assay is based on the use of two monoclonal antibodies specific for epitopes at the C-peptide/insulin A chain junction and at the insulin B chain/C-peptide junction, respectively. Cross-reactivities with insulin, C-peptide, and the four proinsulin conversion intermediates were negligible. The detection limit in buffer was 0.2 pmol/L (3 standard deviations from zero). The working range was 0.2-100 pmol/L. The mean intra- and interassay coefficients of variation were 2.4% and 8.9%, respectively. The mean recovery of added proinsulin was 103%. Dilution curves of 40 serum samples are parallel to the proinsulin calibration curve. Proinsulin concentrations in 20 fasting healthy subjects were all above the limit of detection: median (range), 2.7 pmol/L (1.1-6.9 pmol/L). Six fasting non-insulin-dependent diabetes mellitus and five insulinoma patients had proinsulin concentrations significantly higher than healthy subjects: median (range), 7.7 pmol/L (3.2-18 pmol/L) and 153 pmol/L (98-320 pmol/L), respectively.

Adult↗
PubMed1997

Stability of insulin lispro in insulin infusion systems.

OBJECTIVE: To test stability of insulin lispro in two insulin infusion systems over 48 h. RESEARCH DESIGN AND METHODS: We used reverse-phase and size-exclusion high-performance liquid chromatography (HPLC) to determine the purity, potency, and degree of polymerization of U100 insulin lispro (Humalog) after 24- and 48-h pump cycles conducted at 37 degrees C in five Disetronic H-TRON V100 and five MiniMed 504 pumps. Pumps were set to deliver a basal rate of 0.5 U/h and 6-U boluses at t = 0, 4, 8, 24, 24.5, 28.5, 32.5, and 48 h during each cycle. The effluent was collected into 1-ml vials, pooled at 24 or 48 h, and stored at 4 degrees C until assay. After each 48-h run period of insulin delivery, assays for potency, polymer, and purity were performed on the pooled samples from each individual cycle. m-cresol content and the pooled reservoir content were assayed in the 48-h pooled samples. RESULTS: Insulin lispro retained full HPLC potency (delta < or = 4%) at 48 h, with no degradation of insulin lispro to des-amidoinsulin forms (24 or 48 h). No increase in pumped insulin polymer concentration was observed following 24 h of pump flow. Nonsignificant increases of < or =0.09% (Disetronic) and < or =0.15% (MiniMed) from initial concentrations of 0.18% (polymer divided by total insulin) were detected in three of five pump cycles at 48 h when compared with 37 degrees C paired controls. Nonsignificant decreases (<5 and 10%, Disetronic and MiniMed, respectively) of m-cresol content occurred in both systems following 48 h storage in each device, but sterility was not compromised by this decrease (initial m-cresol concentration, 3.15 mg/ml). Pump performance was without mechanical or electrical fault throughout the study Basal and bolus insulin delivery was evaluated three times daily and remained as expected. Occlusion of catheters by insulin precipitation did not occur, and no change in pH was observed following delivery. CONCLUSIONS: We conclude that insulin lispro is suitable for prolonged infusion in these two medical devices when syringes and catheters are replaced at 48-h intervals.

Chromatography, High Pressure Liquid↗
PubMed1997

Hospital-based physicians--independent contractor or ?

The attack by the Internal Revenue Service on the classification of workers who operate as independent contractors has continued unabated over the last nine years, and despite increased congressional concern regarding the Internal Revenue Service's handling of independent contractor audits, every business that utilizes the services of independent contractors should assume that they, in time, will be audited by the Internal Revenue Service.

Contract Services↗
PubMed1996

Mapping the functional surface of insulin by design: structure and function of a novel A-chain analogue.

Functional surfaces of a protein are often mapped by combination of X-ray crystallography and mutagenesis. Such studies of insulin have yielded paradoxical results, suggesting that the native state is inactive and reorganizes on receptor binding. Of particular interest is the N-terminal alpha-helix of the A-chain. Does this segment function as an alpha-helix or reorganize as recently proposed in a prohormone-convertase complex? To correlate structure and function, we describe a mapping strategy based on protein design. The solution structure of an engineered monomer ([AspB10, LysB28, ProB29]-human insulin) is determined at neutral pH as a template for synthesis of a novel A-chain analogue. Designed by analogy to a protein-folding intermediate, the analogue lacks the A6-A11 disulphide bridge; the cysteine residues are replaced by serine. Its solution structure is remarkable for segmental unfolding of the N-terminal A-chain alpha-helix (A1 to A8) in an otherwise native subdomain. The structure demonstrates that the overall orientation of the A and B chains is consistent with reorganization of the A-chain's N-terminal segment. Nevertheless, the analogue's low biological activity suggests that this segment, a site of clinical mutation causing diabetes mellitus, functions as a preformed recognition alpha-helix.

Amino Acid Sequence↗
PubMed1996

Structure and dynamics of a protein assembly. 1H-NMR studies of the 36 kDa R6 insulin hexamer.

The structure and dynamics of the R6 human insulin hexamer are investigated by two- and three-dimensional homonuclear 1H-NMR spectroscopy. The R6 hexamer, stabilized by Zn2+ and phenol, provides a model of an allosteric protein assembly and is proposed to mimic aspects of receptor recognition. Despite the large size of the assembly (36 kDa), its extreme thermal stability permits high-resolution spectra to be observed at 55 degrees C. Each spin system is represented uniquely, implying either 6-fold symmetry or fast exchange among allowed protomeric conformations. Dramatic changes in chemical shifts and long-range nuclear Overhauser enhancements (NOEs) are observed relative to the spectra of insulin monomers. Complete sequential assignment is obtained and demonstrates native secondary structure with distinctive R-state N-terminal extension of the B-chain alpha-helix (residues B1 to B19). The distance-geometry structure of an R-state promoter is similar to those of R6 crystal structures. Specific long-range intra- and intersubunit NOEs, assigned by stepwise analysis of engineered insulin monomer and dimers, demonstrate that tertiary and quaternary contacts are also similar. Although the hexamer is well-ordered in solution, binding of phenol to an internal cavity occurs within milliseconds, implying the existence of "gatekeeper" residues whose flexibility provides a portal of entry and release. Changes in 1H-NMR chemical shifts on hexamer assembly are readily rationalized by analysis of aromatic ring-currents and provide sensitive probes for sites of protein-protein interaction and phenol binding. Our results provide a foundation for the interaction and phenol binding. Our results provide a foundation for the studies of insulin analogues (such as "designed" insulins of therapeutic interest) under conditions of clinical formulation and for the investigation of the effects of protein assembly on the dynamics of individual protomers.

Circular Dichroism↗
PubMed1995

Role of C-terminal B-chain residues in insulin assembly: the structure of hexameric LysB28ProB29-human insulin.

BACKGROUND: LysB28ProB29-human insulin (Humalog), a fully potent insulin analog in which the prolyl, lysyl sequence at the C-terminal end of the B-chain is inverted, exhibits a decreased association of monomers to dimers leading to rapid in vivo absorption. This provides important benefits for the insulin-requiring diabetic. In spite of its monomeric nature, LysB28ProB29-human insulin can exist as a discrete hexameric structure in the presence of both zinc and phenol. Studies of the crystal structure of LysB28ProB29-human insulin in a hexameric complex were initiated to gain a molecular understanding of the effect of the sequence inversion on the analog's self-association properties and, consequently, its in vivo efficacy. RESULTS: Under the conditions reported, LysB28ProB29-human insulin crystallized as a T3Rf3 hexamer that is isomorphous with the uncomplexed T3Rf3 native human insulin hexamer previously known as '4Zn insulin'. The three-dimensional structure of the T3Rf3 hexamer was determined by X-ray crystallographic methods to a resolution of 2.3 A. The prolyl, lysyl sequence inversion leads to local conformational changes at the C termini of the B-chains which eliminate two critical hydrophobic interactions and weaken two terminal beta-sheet hydrogen bonds that stabilize the dimer. CONCLUSIONS: The loss of these native dimer interactions weakens the hexameric LysB28ProB29-human insulin complex formed in the presence of phenolic ligands. Thus, it is hypothesized that the diffusion of the phenolic ligands from the site of injection results in the dissociation of hexamers directly to monomers, thereby maintaining the rapid time-action of the monomeric analog in spite of the hexameric conformation in therapeutic formulations.

Amino Acid Sequence↗