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H W Detrich

Publications and source records attributed to H W Detrich.

At least 37 records · Page 2Linked to original sources
PubMed1992

Brain and egg tubulins from antarctic fishes are functionally and structurally distinct.

The multitubulin hypothesis proposes that chemically distinct tubulins may possess different polymerization properties or may form functionally different microtubules. To test this hypothesis, we have examined the functional properties and the structures of singlet-specific nonneural and neural tubulins from Antarctic fishes. Tubulins were purified from eggs of Notothenia coriiceps neglecta, and from brain tissues of N. coriiceps neglecta or N. gibberifrons, by DEAE ion-exchange chromatography and cycles of microtubule assembly/disassembly. At temperatures between 0 and 20 degrees C, each of these tubulins polymerized efficiently in vitro to yield microtubules of normal morphology. Critical concentrations for polymerization of egg tubulin ranged from 0.057 mg/ml at 3 degrees C to 0.002 mg/ml at 18 degrees C, whereas those for brain tubulin at like temperatures were 4-10-fold larger. Polymerization of both tubulins was entropically driven, but the apparent standard enthalpy and entropy changes for microtubule elongation by egg tubulin (delta Happ0 = +33.9 kcal/mol, delta Sapp0 = +151 entropy units) were significantly greater than values observed for brain tubulin (delta Happ0 = +26.5 kcal/mol, delta Sapp0 = +121 entropy units). Egg tubulin was composed of approximately six alpha and two beta chains and lacked the beta III isotype, whereas brain tubulin was more complex (greater than or equal to 10 of each chain type). Furthermore, egg alpha tubulins were more basic, and their carboxyl termini more resistant to cleavage by subtilisin, than were the alpha chains of brain. We conclude that brain and egg tubulins from the Antarctic fishes are functionally distinct in vitro, due either to qualitative or quantitative differences in isotypic composition, to differential posttranslational modification of shared isotypes, or to both.

Animals↗
PubMed1992

Colchicine-binding sites of brain tubulins from an antarctic fish and from a mammal are functionally similar, but not identical: implications for microtubule assembly at low temperature.

The tubulins of Antarctic fishes possess adaptations that favor microtubule formation at low body temperatures (Detrich et al.: Biochemistry 28:10085-10093, 1989). To determine whether some of these adaptations may be present in a domain of tubulin that participates directly or indirectly in lateral contact between microtubule protofilaments, we have examined the energetics of the binding of colchicine, a drug thought to bind to such a site, to pure brain tubulins from an Antarctic fish (Notothenia gibberifrons) and from a mammal (the cow, Bos taurus). At temperatures between 0 and 20 degrees C, the affinity constants for colchicine binding to the fish tubulin were slightly smaller (1.5-2.6-fold) than those for bovine tubulin. van't Hoff analysis showed that the standard enthalpy changes for colchicine binding to the two tubulins were comparable (delta H degrees = +10.6 and +7.4 kcal mol-1 for piscine and bovine tubulins, respectively), as were the standard entropy changes (delta S degrees = +61.3 eu for N. gibberifrons tubulin, +51.2 eu for bovine tubulin). At saturating concentrations of the ligand, the maximal binding stoichiometry for each tubulin was approximately 1 mol colchicine/mol tubulin dimer. The data indicate that the colchicine-binding sites of the two tubulins are similar, but probably not identical, in structure. The apparent absence of major structural modifications at the colchicine site suggests that this region of tubulin is not involved in functional adaptation for low-temperature polymerization. Rather, the colchicine site of tubulin may have been conserved evolutionarily to serve in vivo as a receptor for endogenous molecules (i.e., "colchicine-like" molecules or MAPs) that regulate microtubule assembly.

Animals↗
PubMed1990

Microtubule-associated proteins from Antarctic fishes.

Microtubules and presumptive microtubule-associated proteins (MAPs) were isolated from the brain tissues of four Antarctic fishes (Notothenia gibberifrons, N. coriiceps neglecta, Chaenocephalus aceratus, and a Chionodraco sp.) by means of a taxol-dependent, microtubule-affinity procedure (cf. Vallee: Journal of Cell Biology 92:435-442, 1982). MAPs from these fishes were similar to each other in electrophoretic pattern. Prominent in each preparation were proteins in the molecular weight ranges 410,000-430,000, 220,000-280,000, 140,000-155,000, 85,000-95,000, 40,000-45,000, and 32,000-34,000. The surfaces of MAP-rich microtubules were decorated by numerous filamentous projections. Exposure to elevated ionic strength released the MAPs from the microtubules and also removed the filamentous projections. Addition of fish MAPs to subcritical concentrations of fish tubulins at 0-5 degrees C induced the assembly of microtubules. Both the rate and the extent of this assembly increased with increasing concentrations of the MAPs. Sedimentation revealed that approximately six proteins, with apparent molecular weights between 60,000 and 300,000, became incorporated into the microtubule polymer. Bovine MAPs promoted microtubule formation by fish tubulin at 2-5 degrees C, and proteins corresponding to MAPs 1 and 2 co-sedimented with the polymer. MAPs from C. aceratus also enhanced the polymerization of bovine tubulin at 33 degrees C, but the microtubules depolymerized at 0 degrees C. We conclude that MAPs are part of the microtubules of Antarctic fishes, that these proteins promote microtubule assembly in much the same way as mammalian MAPs, and that they do not possess special capacities to promote microtubule assembly at low temperatures or to prevent cold-induced microtubule depolymerization.

Alkaloids↗
PubMed1990

An antifreeze glycopeptide gene from the antarctic cod Notothenia coriiceps neglecta encodes a polyprotein of high peptide copy number.

The antarctic fish Notothenia coriiceps neglecta synthesizes eight antifreeze glycopeptides (AFGP 1-8; Mr 2600-34,000) to avoid freezing in its ice-laden freezing habitat. We report here the sequence of one of its AFGP genes. The structural gene contains 46 tandemly repeated segments, each encoding one AFGP peptide plus a 3-amino acid spacer. Most of the repeats (44/46) code for peptides of AFGP 8; the remaining 2 code for peptides of AFGP 7. At least 2 of the 3 amino acids in the spacers could act as substrate for chymotrypsin-like proteases. The nucleotide sequence between the translation initiation codon (ATG) and the first AFGP-coding segment is G + T-rich and encodes a presumptive 37-residue signal peptide of unusual sequence. Primer extension establishes the transcription start site at nucleotide 43 upstream from ATG. CAAT and TATA boxes begin at nucleotides 53 and 49, respectively, upstream from the transcription start site. The polyadenylylation signal, AATAAA, is located approximately 240 nucleotides downstream from the termination codon. A mRNA (approximately 3 kilobases) was found that matches the size of this AFGP gene. Thus, this AFGP gene encodes a secreted, high-copy-number polyprotein that is processed posttranslationally to produce active AFGPs.

Amino Acid Sequence↗
PubMed1989

Polymerization of Antarctic fish tubulins at low temperatures: energetic aspects.

Tubulins were purified from the brain tissues of three Antarctic fishes, Notothenia gibberifrons, Notothenia coriiceps neglecta, and Chaenocephalus aceratus, by ion-exchange chromatography and one cycle of temperature-dependent microtubule assembly and disassembly in vitro, and the functional properties of the protein were examined. The preparations contained the alpha- and beta-tubulins and were free of microtubule-associated proteins. At temperatures between 0 and 24 degrees C, the purified tubulins polymerized readily and reversibly to yield both microtubules and microtubule polymorphs (e.g., "hooked" microtubules and protofilament sheets). Critical concentrations for polymerization of the tubulins ranged from 0.87 mg/mL at 0 degrees C to 0.02 mg/mL at 18 degrees C. The van't Hoff plot of the apparent equilibrium constant for microtubule elongation at temperatures between 0 and 18 degrees C was linear and gave a standard enthalpy change (delta H degree) of +26.9 kcal/mol and a standard entropy change (delta S degree) of +123 eu. At 10 degrees C, tubulin from N. gibberifrons polymerized efficiently at high ionic strength; the critical concentration increased monotonically from 0.041 to 0.34 mg/mL as the concentration of NaCl added to the assembly buffer was increased from 0 to 0.4 M. Together, the results indicate that the polymerization of tubulins from the Antarctic fishes is entropically driven and suggest that an increased reliance on hydrophobic interactions underlies the energetics of microtubule formation at low temperatures. Thus, evolutionary modification to increase the proportion of hydrophobic interactions (relative to other bond types) at sites of interdimer contact may be one adaptive mechanism that enables the tubulins of cold-living poikilotherms to polymerize efficiently at low temperatures.

Animals↗
PubMed1989

Dynamics of Antarctic fish microtubules at low temperatures.

The tubulins of Antarctic fishes, purified from brain tissue and depleted of microtubule-associated proteins (MAPs), polymerized efficiently in vitro to yield microtubules at near-physiological and supraphysiological temperatures (5, 10, and 20 degrees C). The dynamics of the microtubules at these temperatures were examined through the use of labeled guanosine 5'-triphosphate (GTP) as a marker for the incorporation, retention, and loss of tubulin dimers. Following attainment of a steady state in microtubule mass at 20 degrees C, the rate of incorporation of [3H]GTP (i.e., tubulin dimers) during pulses of constant duration decreased asymptotically toward a constant, nonzero value as the interval prior to label addition to the microtubule solution increased. Concomitant with the decreasing rate of label incorporation, the average length of the microtubules increased, and the number concentration of microtubules decreased. Thus, redistribution of microtubule lengths (probably via dynamic instability and/or microtubule annealing) appears to be responsible for the time-dependent decrease in the rate of tubulin uptake. When the microtubules had attained both a steady state in mass and a constant length distribution, linear incorporation of labeled tubulin dimers over time occurred at rates of 1.45 s-1 at 5 degrees C, 0.48 s-1 at 10 degrees C, and 0.18 s-1 at 20 degrees C. Thus, the microtubules displayed greater rates of subunit flux, or treadmilling, at lower, near-physiological temperatures. At each temperature, most of the incorporated label was retained by the microtubules during a subsequent chase with excess unlabeled GTP.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Antarctic fish tubulins: heterogeneity, structure, amino acid compositions and charge.

1. Tubulins purified from the brain tissues of three Antarctic fishes (Notothenia gibberifrons, Notothenia coriiceps neglecta, and Chaenocephalus aceratus) contain equimolar quantities of the alpha and beta chains and are free of microtubule-associated proteins (MAPs) and other non-tubulin proteins. 2. When examined by isoelectric focusing and by two-dimensional electrophoresis, brain tubulins from the Antarctic fishes were found to be highly heterogeneous; each was resolved into 15-20 distinct variants. The range of isoelectric points displayed by the Antarctic fish tubulins (5.30-5.75) is slightly more basic than that of bovine brain tubulin (5.25-5.60). 3. Peptide mapping demonstrated that tubulins from the Antarctic fishes and the cow differ in structure. 4. The amino acid compositions of piscine and mammalian tubulins are similar, but the Antarctic fish tubulins apparently contain fewer glutamyl and/or glutaminyl residues than do tubulins from the temperate channel catfish (Ictalurus punctatus) and the cow. 5. Native tubulin from N. coriiceps neglecta possesses 1-2 fewer net negative charges per tubulin dimer than does bovine tubulin. 6. We suggest that the enhanced assembly of Antarctic fish tubulins at low temperatures (-2 to +2 degrees C) results from adaptive, perhaps subtle, changes in their tubulin subunits.

Adaptation, Physiological↗
PubMed1987

Cold-stable microtubules from Antarctic fishes contain unique alpha tubulins.

The cytoplasmic microtubules of Antarctic fishes assemble from their tubulin subunits at physiological body temperatures in the range -2 to +2 degrees C. Our objective is to determine the structural features that enhance the assembly of Antarctic fish tubulins at low temperatures. Here we compare the structures of tubulin subunits from three Antarctic fishes (Notothenia gibberifrons, Notothenia coriiceps neglecta, and Chaenocephalus aceratus), from three temperate fishes (the dogfish shark Mustelus canis, the channel catfish Ictalurus punctatus, and the goosefish Lophius americanus), and from a mammal (the cow Bos taurus). When reduced, carboxymethylated, and examined by polyacrylamide gel electrophoresis, multiple alpha chains were observed in tubulins from the Antarctic fishes, the catfish, and the goosefish; dogfish and bovine alpha tubulins migrated as single components on this gel system. Prominent in the Antarctic fish tubulins was an alpha variant that migrated more rapidly than the bovine alpha chain; smaller amounts of a rapidly migrating alpha chain were also present in catfish and goosefish tubulins. The beta tubulins of the fishes, with the exception of the goosefish, resolved into major and minor variants with mobilities similar to those of beta 1 and beta 2 tubulins from bovine brain. Peptide mapping demonstrated that the alpha tubulins of Antarctic fishes were similar in structure, yet differed from the alpha chains of the dogfish and the cow (which, in turn, were similar to each other). In contrast, the beta tubulins from these organisms gave peptide patterns of near identity. Finally, the alpha chains of native tubulins from N. coriiceps neglecta and the cow differed in the sensitivity of their C-terminal domains to digestion by subtilisin. These results demonstrate that the alpha tubulins of Antarctic fishes (but not their beta chains) differ structurally from those of temperate fishes and a mammal.

Animals↗
PubMed1986

Heterogeneity and structure of brain tubulins from cold-adapted Antarctic fishes. Comparison to brain tubulins from a temperate fish and a mammal.

Tubulins purified from brain tissue of Antarctic fishes assemble in vitro to form microtubules at the low temperatures experienced by these extreme psychrophiles (Williams, R. C., Jr., Correia, J. J., and DeVries, A. L. (1985) Biochemistry 24, 2790-2798). We have initiated studies to determine the structural requirements for assembly of Antarctic fish tubulins at low temperatures. As a first step we have compared the heterogeneity, structures, amino acid compositions, and net charge of brain tubulins purified from three Antarctic fishes (Notothenia gibberifrons, Notothenia coriiceps neglecta, and Chaenocephalus aceratus), from the temperate channel catfish (Ictalurus punctatus), and from a mammal (the cow). Each preparation contained the alpha- and beta-tubulins and was free of microtubule-associated proteins. When examined by isoelectric focusing and by two-dimensional electrophoresis, brain tubulins from the Antarctic fishes were found to be highly heterogeneous; each was resolved into approximately 20 isoelectric variants. The distributions of the isotubulins from the cold-adapted fishes were similar but differed significantly from those of tubulins from catfish and cow. The average isoelectric points of the alpha- and beta-tubulins from the Antarctic fishes were more basic than the isoelectric points of the corresponding tubulins from bovine brain. Peptide mapping confirmed that tubulins from the Antarctic fishes and the mammal differed in structure. The amino acid compositions of fish and mammalian tubulins were similar, but Antarctic fish tubulins apparently contained fewer Glx residues than did catfish or bovine tubulins. Finally, native tubulins from an Antarctic fish and the cow differed slightly in net negative charge. Thus, brain tubulins from the cold-adapted fishes differ structurally from the tubulins of a temperate fish and of a mammal.

Acclimatization↗
PubMed1986

Mechanism of assembly of sea urchin egg tubulin.

Tubulin purified from eggs of the sea urchin Strongylocentrotus purpuratus assembles efficiently in vitro to form microtubules at physiological (18 degrees C) and nonphysiological (37 degrees C) temperatures. MAPs, ring oligomers, and high concentrations of nonphysiological solvents are not required for the assembly reaction. At concentrations above 1.2 mg/ml at 18 degrees C and 0.5 mg/ml at 37 degrees C a concentration-dependent overshoot in turbidity and in light scattering at small angles was observed: turbidity and scattering increased rapidly to a peak, then decreased asymptotically toward a steady-state value. Electron microscopic analysis demonstrated that tubulin sheets were prevalent during the initial stages of overshoot assembly, whereas complete microtubules were present at steady state. Qualitative observations of solution birefringence suggested that the polymer became progressively more aligned during assembly. The overshoot cannot be explained by proteolysis or denaturation of tubulin, by depletion of GTP, by a decrease in assembled mass, or by redistribution of polymer lengths. Taken together, the results suggest that changes in the form and/or in the organization of the assembling polymer are responsible for the overshoots in turbidity and in light scattering at small angles. Our results are consistent with models of microtubule assembly that postulate nucleation by tubulin sheets and subsequent folding of the sheets to form mature microtubules.

Animals↗
PubMed1985

Mechanism of microtubule assembly. Changes in polymer structure and organization during assembly of sea urchin egg tubulin.

Assembly of tubulin, purified from eggs of the sea urchin Stronglyocentrotus purpuratus, was examined at physiological (18 degrees C) and nonphysiological (37 degrees C) temperatures. Critical concentrations for assembly were 0.71 mg/ml at 18 degrees C and 0.21 mg/ml at 37 degrees C. At tubulin concentrations above 1.2 mg/ml at 18 degrees C and 0.5 mg/ml at 37 degrees C, a concentration-dependent "overshoot" in turbidity and in small-angle light scattering was observed; turbidity and scattering increased rapidly to a peak, then decreased asymptotically toward a steady-state value. Quantitative sedimentation analysis revealed that the mass of assembled polymer reached and maintained a constant level during overshoot of turbidity. Changes in the wavelength dependence of turbidity were consistent with the initial formation of sheets of tubulin, followed by conversion of the sheets to microtubules, both at 18 and 37 degrees C. Examination by negative-stain electron microscopy showed that sheetlike structures predominated during the early stages of overshoot assembly, while complete microtubules were present at steady state. Furthermore, measurements of average polymer length revealed that the overshoots in turbidity and in light scattering are unlikely to be caused by polymer length redistribution. Qualitative observations of solution birefringence suggested that the polymer became progressively more aligned during assembly. These results suggest that the turbidity/light-scattering overshoots reflect changes in the form or in the organization of the assembling polymer, or both.

Animals↗
PubMed1984

Colchicine-binding activity distinguishes sea urchin egg and outer doublet tubulins.

The colchicine-binding activity of tubulin has been utilized to distinguish the tubulins from two distinct microtubule systems of the same species, the sea urchin Strongylocentrotus purpuratus. We have analyzed the colchicine-binding affinities of highly purified tubulins from the unfertilized eggs and from the flagellar outer doublet microtubules by van't Hoff analysis, and have found significant differences in the free energy, enthalpy, and entropy changes characterizing the binding of colchicine to the two tubulins. The data indicate that significant chemical differences in the tubulins from the two functionally distinct microtubule systems exist, and that the differences are expressed in the native forms of the tubulins. Our findings are discussed in terms of the possibility that the colchicine-binding site may be an important regulatory site on the tubulin molecule.

Animals↗
PubMed1983

Purification, characterization, and assembly properties of tubulin from unfertilized eggs of the sea urchin Strongylocentrotus purpuratus.

Tubulin was purified from unfertilized eggs of the sea urchin Strongylocentrotus purpuratus by chromatography of an egg supernatant fraction on DEAE-Sephacel or DEAE-cellulose followed by cycles of temperature-dependent microtubule assembly and disassembly in vitro. After two assembly cycles, the microtubule protein consisted of the alpha- and beta-tubulins (greater than 98% of the protein) and trace quantities of seven proteins with molecular weights less than 55 000; no associated proteins with molecular weights greater than tubulin were observed. When analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis on urea-polyacrylamide gradient gels, the alpha- and beta-tubulins did not precisely comigrate with their counterparts from bovine brain. Two-dimensional electrophoresis revealed that urchin egg tubulin contained two major alpha-tubulins and a single major beta species. No oligomeric structures were observed in tubulin preparations maintained at 0 degrees C. Purified egg tubulin assembled efficiently into microtubules when warmed to 37 degrees C in a glycerol-free polymerization buffer containing guanosine 5'-triphosphate. The critical concentration for assembly of once- or twice-cycled egg tubulin was 0.12-0.15 mg/mL. Morphologically normal microtubules were observed by electron microscopy, and these microtubules were depolymerized by exposure to low temperature or to podophyllotoxin. Chromatography of a twice-cycled egg tubulin preparation on phosphocellulose did not alter its protein composition and did not affect its subsequent assembly into microtubules. At concentrations above 0.5-0.6 mg/mL, a concentration-dependent "overshoot" in turbidity was observed during the assembly reaction. These results suggest that egg tubulin assembles into microtubules in the absence of the ring-shaped oligomers and microtubule-associated proteins that characterize microtubule protein from vertebrate brain.

Animals↗
PubMed1982

Characteristics of leucine transport by isolated hepatocytes of Antarctic fish at low temperatures.

Hepatocytes prepared by collagenase perfusion from Antarctic nototheniid fish of genus Trematomus are active in uptake of [14C]leucine at 0, 5, and 10 degrees C. The system is saturable with apparent Km about 1.0 mM. Isoleucine and phenylalanine were major competitors, valine was about one-half as effective, while alanine, glycine and histidine had no effect. Temperature dependency of rates in the 0-10 degrees C range yielded Ea = 65 kJ/mol (Q10 = 2.7). The average first-order rate constant at 0 degrees C was 0.1 min-1, one-third the value of 0.3 min-1 estimated for clearance of [14C]leucine by liver of these species in vivo. Affinity and specificity agreed well with in vivo data on liver clearance of leucine, both in Antarctic fish at 0 degrees C and in temperate fish acclimated to 10 degrees C and 20 degrees C. The results indicate similar modifications of leucine transport associated with evolutionary cold adaptation and seasonal acclimation in fish.

Amino Acids↗
PubMed1982

Effect of colchicine binding on the reversible dissociation of the tubulin dimer.

The reversible subunit-dissociation equilibria of the tubulin alpha beta dimer and of the colchicine-tubulin dimer complex have been examined by equilibrium ultracentrifugation at 4.6 degrees C. The dissociation constants (KD) of tubulin from bovine brain and from flagellar outer-doublet microtubules of the sea urchin Strongylocentrotus purpuratus were 7.4 x 10(-7) M and 15.2 x 10(-7) M, respectively. In contrast, both brain and outer-doublet colchicine-tubulin complexes dissociated less readily into their alpha- and beta-tubulin monomers; KD = 2.7 x 10(-7) M for the brain complex and KD = 5.0 x 10(-7) M for the outer-doublet colchicine-tubulin species. Podophyllotoxin (2 x 10(-4) M), tropolone (10(-4) M), or both podophyllotoxin and tropolone (2 x 10(-4) and 5 x 10(-4) M, respectively) had no effect on the dissociation constant of brain tubulin. Under these experimental conditions, the initial colchicine-binding capacities of brain and flagellar tubulins were 0.87 +/- 0.05 and 0.70 +/- 0.07 mol/mol, respectively. The colchicine-binding activities of free tubulins decayed at 4 degrees C according to first-order kinetics with half-times of 37 h for brain tubulin and 26 h for flagellar tubulin. However, colchicine-tubulin complexes (brain or flagellar) showed no decay of binding activity when stored at 4 degrees C for periods up to 4 days. These results strongly support the following conclusions: (1) colchicine binding induces or stabilizes a conformational isomer of tubulin that dissociates into its alpha and beta monomers less readily than free tubulin; (2) the conformational change in tubulin is specific for binding of the intact colchicine molecule and does not occur when ligands specific for the trimethoxyphenyl subdomain (i.e., podophyllotoxin) or tropolone subdomain of the colchicine-binding site bind singly or simultaneously to tubulin; and (3) bound colchicine stabilizes tubulin against loss of colchicine-binding activity at 4 degrees C. This altered conformation of tubulin may be involved in the substoichiometric poisoning of microtubule assembly produced by the addition of colchicine-tubulin complexes to the ends of microtubules.

Animals↗
PubMed1981

Changes in the circular dichroic spectrum of colchicine associated with its binding to tubulin.

Circular dichroism has been used to study the interaction of colchicine with the tubulin alpha beta dimer at 26 degrees C. Tubulin purified from bovine brain microtubule protein exhibits negligible circular dichroism at wavelengths above 310 nm. Free colchicine exhibits a negative circular dichroic band at 340 nm characterized by an extremum in molar ellipticity [theta] of -3.35 (+/- 0.27) x 10(4) deg.cm2/dmol. This negative band either vanished or was greatly reduced, i.e., [theta] = 0 (+/- 0.57) x 10(4) deg.cm2/dmol, when colchicine was bound to tubulin. This was demonstrated by circular dichroic studies on stable [3H]colchicine-tubulin complexes which were separated from all unbound colchicine by means of gel filtration. Also, tubulin was titrated with colchicine, and at low colchicine concentrations, the observed ellipticity at 340 nm could be extrapolated to zero at 0 M colchicine; saturation occurred at a molar ratio of colchicine to tubulin of about 1:1. The association constant characterizing the drug-protein interaction was estimated to be about 0.9 micro M-1. As controls, three other acidic proteins were studied at a molar ratio of colchicine to protein of 2:1, and their presence had no effect on the circular dichroic properties of colchicine. These results are consistent with the idea that a conformational change in colchicine accompanies its binding to tubulin. The spectrum of the complex between 250 and 300 nm was quite similar to that expected from simple additivity of the spectra of drug and protein except between 255 and 265 nm. The technique described herein should be applicable to other protein-drug systems.

Animals↗