Showing papers on "Circular dichroism published in 1998"
TL;DR: Results indicate that the A state of PI3-SH3 is partially folded and support the hypothesis that partially folded states formed in solution are precursors of amyloid deposition.
Abstract: The SH3 domain is a well characterized small protein module with a simple fold found in many proteins. At acid pH, the SH3 domain (PI3-SH3) of the p85α subunit of bovine phosphatidylinositol 3-kinase slowly forms a gel that consists of typical amyloid fibrils as assessed by electron microscopy, a Congo red binding assay, and x-ray fiber diffraction. The soluble form of PI3-SH3 at acid pH (the A state by a variety of techniques) from which fibrils are generated has been characterized. Circular dichroism in the far- and near-UV regions and 1H NMR indicate that the A state is substantially unfolded relative to the native protein at neutral pH. NMR diffusion measurements indicate, however, that the effective hydrodynamic radius of the A state is only 23% higher than that of the native protein and is 20% lower than that of the protein denatured in 3.5 M guanidinium chloride. In addition, the A state binds the hydrophobic dye 1-anilinonaphthalene-8-sulfonic acid, which suggests that SH3 in this state has a partially formed hydrophobic core. These results indicate that the A state is partially folded and support the hypothesis that partially folded states formed in solution are precursors of amyloid deposition. Moreover, that this domain aggregates into amyloid fibrils suggests that the potential for amyloid deposition may be a common property of proteins, and not only of a few proteins associated with disease.
662 citations
TL;DR: An unprecedented small thioaurite cluster compound (with metallic Au0 core) has been isolated in high yield by decomposition of polymeric Au(I)SG compounds, where GSH is the ubiquitous tripeptide glutathione, N-γ-glutamyl-cysteinyl-glycine.
Abstract: An unprecedented small thioaurite cluster compound (with metallic Au0 core) has been isolated in high yield by decomposition of polymeric Au(I)SG compounds, where GSH is the ubiquitous tripeptide glutathione, N-γ-glutamyl-cysteinyl-glycine The Au:SG clusters appear to share the high stability and robustness of their hydrophobic n-alkyl analogues but are highly water soluble The most abundant cluster produced by these methods can be easily separated from its homologues by gel electrophoresis Its total molecular weight is ca 104 kDa, and the mass of its strongly bound inorganic core is 56 kDa, suggesting the composition Au28(SG)16 This composition is also consistent with the X-ray diffraction pattern of the crystalline molecular solid Distinct features in the optical absorption spectroscopy are inherently different from either larger clusters or smaller gold cluster compounds The compound is optically active, as evidenced by circular dichroism in the near-IR, visible, and near-UV regions The 13C N
642 citations
TL;DR: A cooperative transition from disordered to helical structure is observed as the peptide concentration is increased, consistent with formation of an oligomer, and the extent of α-helicity correlates with the antibacterial activity of LL-37 against both Gram-positive and Gram-negative bacteria.
626 citations
TL;DR: It is demonstrated by CD and tryptophan fluorescence spectroscopy that copper induces changes to the tertiary structure of SHaPrP(29-231) and proposed that the binding of two copper ions to four octarepeats induces a more defined structure to this region.
Abstract: The infectious isoform of the prion protein (PrPSc) is derived from cellular PrP (PrPC) in a conversion reaction involving a dramatic reorganization of secondary and tertiary structure. While our understanding of the pathogenic role of PrPSc has grown, the normal physiologic function of PrPC still remains unclear. Using recombinant Syrian hamster prion protein [SHaPrP(29-231)], we investigated metal ions as possible ligands of PrP. Near-UV circular dichroism spectroscopy (CD) indicates that the conformation of SHaPrP(29-231) resembles PrPC purified from hamster brain. Here we demonstrate by CD and tryptophan (Trp) fluorescence spectroscopy that copper induces changes to the tertiary structure of SHaPrP(29-231). Binding of copper quenches the Trp fluorescence emission significantly, shifts the emission spectrum to shorter wavelengths, and also induces changes in the near-UV CD spectrum of SHaPrP(29-231). The binding sites are highly specific for Cu2+, as indicated by the lack of a change in Trp fluorescence emission with Ca2+, Co2+, Mg2+, Mn2+, Ni2+, and Zn2+. Binding of Cu2+ also promotes the conformational shift from a predominantly alpha-helical to a beta-sheet structure. Equilibrium dialysis experiments indicate a binding stoichiometry of approximately 2 copper molecules per PrP molecule at physiologically relevant concentrations, and pH titration of Cu2+ binding suggests a role for histidine as a chelating ligand. NMR spectroscopy has recently demonstrated that the octarepeats (PHGGGWGQ) in SHaPrP(29-231) lack secondary or tertiary structure in the absence of Cu2+. Our results suggest that each Cu2+ binds to a structure defined by two octarepeats (PHGGGWGQ) with one histidine and perhaps one glycine carbonyl chelating the ion. We propose that the binding of two copper ions to four octarepeats induces a more defined structure to this region.
525 citations
TL;DR: In the absence of surfactants, recombinant human growth hormone (rhGH) rapidly forms insoluble aggregates during agitation, and the nonionic surfactant Tween 20, when present at Tween:protein molar ratios >4, effectively inhibits this aggregation.
311 citations
TL;DR: Experimental and theoretical studies of the structural properties of chiral peptoids lay the groundwork for the rational design of more complex polypeptoid molecules, with a variety of applications, ranging from nanostructures to nonviral gene delivery systems.
Abstract: Polymers of N-substituted glycines (“peptoids”) containing chiral centers at the α position of their side chains can form stable structures in solution. We studied a prototypical peptoid, consisting of five para-substituted (S)-N-(1-phenylethyl)glycine residues, by NMR spectroscopy. Multiple configurational isomers were observed, but because of extensive signal overlap, only the major isomer containing all cis-amide bonds was examined in detail. The NMR data for this molecule, in conjunction with previous CD spectroscopic results, indicate that the major species in methanol is a right-handed helix with cis-amide bonds. The periodicity of the helix is three residues per turn, with a pitch of ≈6 A. This conformation is similar to that anticipated by computational studies of a chiral peptoid octamer. The helical repeat orients the amide bond chromophores in a manner consistent with the intensity of the CD signal exhibited by this molecule. Many other chiral polypeptoids have similar CD spectra, suggesting that a whole family of peptoids containing chiral side chains is capable of adopting this secondary structure motif. Taken together, our experimental and theoretical studies of the structural properties of chiral peptoids lay the groundwork for the rational design of more complex polypeptoid molecules, with a variety of applications, ranging from nanostructures to nonviral gene delivery systems.
290 citations
TL;DR: In this article, the second specific metal binding site on human, bovine and porcine albumins Ni(II, Zn(II), Cd(II) was investigated using electron spin resonance spectroscopy.
284 citations
TL;DR: The quantitative and reversible compaction of open circular plasmid DNA into toroids containing one to 19 molecules by sequential treatment with spermine and an excess of uranyl acetate is reported and the toroidal DNA structure was proven by cryoelectron microscopy.
Abstract: The quantitative and reversible compaction of open circular plasmid DNA (7676 bp) into toroids containing one to 19 molecules by sequential treatment with spermine and an excess of uranyl acetate is reported The toroidal DNA structure was proven by cryoelectron microscopy Linearized and supercoiled variants of the DNA also gave toroids under these conditions, but yields were significantly lower In the presence of spermine alone no toroids were found Open circular plasmid B-DNA helix was converted into the C-type helical form upon compaction as was shown by CD spectroscopy (negative peak at 255 nm) and electron microscopy (18-nm interduplex distance instead of 29 nm) Addition of uranyl salt to the DNA−spermine complexes resulted in the formation of netlike assemblies which further compacted to give toroids A model containing a hexagonal arrangement of DNA strands with extensive strand crossings is proposed Curvature and thus toroid formation is thought to be induced by the hydrophobic DNA coating
223 citations
TL;DR: In this article, the authors examined the behavior of elastin-like peptides and found that all lengths of peptide undergo an extended left and right arrow beta-turn transition with increasing temperature, suggesting that the induction of the beta-spiral occurs at the level of single pentameric units.
205 citations
TL;DR: To assess the potential of using porphyrins as probes for these structures, the interaction of tetrakis(4-N-methylpyridyl)porphine (H2TMPyP) with the simple quadruplex formed by T4G4 and with the duplex formed by CGCGATATCGCG is investigated.
Abstract: We have recently reported the cation-induced self-assembly of DNA oligomers of the general sequence C4T4G4T1-4G4 into high-molecular weight multistranded structures [Marotta, S.P., Tamburri, P.A., and Sheardy, R.D. (1996) Biochemistry 35, 10484-10492]. The architecture of the proposed structure consists of a series of four leafed G4 tetrads tethered together via one or two T1-4 strands and thus resembles a long four-sided hollow tube with periodic "pockets". These pockets possess electrostatic, hydrogen bonding, and hydrophobic contact points and should be ideal candidates for the binding of small molecules. To assess the potential of using porphyrins as probes for these structures, we have investigated the interaction of tetrakis(4-N-methylpyridyl)porphine (H2TMPyP) with the simple quadruplex formed by T4G4 and with the duplex formed by CGCGATATCGCG. Visible absorption, circular dichroism, and fluorescent energy transfer studies indicate that H2TMPyP binds to both the duplex and quadruplex via intercalation at low [porphyrin]/[DNA molecule] ratios, i.e., in the presence of excess potential DNA binding sites. Analyses of Scatchard plots show that H2TMpyP binds with high affinity to both DNA secondary structures but binds to the quadruplex with an affinity 2 times greater than that of the duplex.
205 citations
TL;DR: A method based on electrospray ionization (ESI) mass spectrometry to determine solution association constants (KA) for complexes between glycopeptide antibiotics and several peptide ligands and the measured KA values are in good agreement with previously reported values obtained by standard spectroscopic titration techniques.
Abstract: We report a method based on electrospray ionization (ESI) mass spectrometry to determine solution association constants (KA) for complexes between glycopeptide antibiotics (vancomycin and ristocetin) and several peptide ligands. The measured KA values are in good agreement with previously reported values obtained by standard spectroscopic titration techniques. The pH stability of the ristocetin−diacetyl-l-lysyl-d-alanyl-d-alanine complex was investigated by ESI mass spectrometry and circular dichroism (CD) spectroscopy. The two methods produce very similar results, demonstrating that the ESI mass spectra reflect the pH stability of the complex. In solution, the antibiotics bind stereospecifically to peptides containing a C-terminal d-Ala-d-Ala sequence, whereas no complex formation is observed with peptides containing the l-Ala-l-Ala stereoisomer. To investigate whether electrospray ionization is able to reflect the structurally specific interaction between antibiotics and d-Ala-d-Ala peptide ligands, an ...
TL;DR: It is determined that the hydrophobin SC3 from Schizophyllum commune contains 16-22 O-linked mannose residues, probably attached to the N-terminal part of the peptide chain, and that Alpha-helix is induced specifically upon assembly of the protein on a hydrophobic solid surface.
TL;DR: The kinetics of Pi binding show saturation of the rate at high Pi concentrations, and this together with other information suggests a two-step mechanism with the fluorescence change after binding, concomitant with a conformational change of the protein that closes the cleft containing the Pi binding site.
Abstract: The mechanism of Pi interaction with phosphate binding protein of Escherichia coli has been investigated using the A197C mutant protein labeled with a coumarin fluorophore (MDCC-PBP), which gives a fluorescence change on binding Pi. A pure preparation of MDCC-PBP was obtained, in which the only significant inhomogeneity is the presence of equal amounts of two diastereoisomers due to the chiral center formed on reaction of the cysteine with the maleimide. These diastereoisomers could not be separated, but Pi binding data suggest that they differ in affinity and fluorescence change. When Pi binds to MDCC-PBP, the fluorescence quantum yield increases 8-fold and the fluorescence intensity at 465 nm increases 13-fold. The kinetics of Pi binding show saturation of the rate at high Pi concentrations, and this together with other information suggests a two-step mechanism with the fluorescence change after binding, concomitant with a conformational change of the protein that closes the cleft containing the Pi binding site. Cleft closure has a rate constant of 317 s-1 (pH 7.0, 5 degrees C), and opening has a rate constant of 4.5 s-1. The fluorescence increase is likely to arise from a change in the hydrophobic environment during this closure as the steady state fluorescence emission (lambdamax and intensity) on Pi binding is mimicked by the addition of ethanol to aqueous solutions of an MDCC-thiol adduct. Fluorescence lifetimes in the absence and presence of Pi were 0.3 and 2.4 ns, respectively, consistent with the change in quantum yield. The rotational correlation time of the coumarin increases only 2-fold from 15 to 26 ns on binding Pi as measured by time-resolved polarization, consistent with the main rotation being determined by the protein even in the open conformation, but with greater local motion. Circular dichroism of the coumarin induced by the protein is weak in the absence of Pi and increases strongly upon saturation by Pi. These data are also consistent with an open to closed conformational model.
TL;DR: The ability of gangliosides to induce an α-helical structure in Aβ and thereby diminish fibrillogenesis is reported here and it is found that the sialic acid moiety of gang liosides is necessary for the induction of α- Helical structure.
TL;DR: The 9th type III module of murine fibronectin was expressed in E. coli and folded into a compact homogeneous monomer whose unfolding and refolding were then investigated by fluorescence, circular dichroism, calorimetry and electron microscopy as discussed by the authors.
TL;DR: In this article, the chiroptical properties of planar-chiral and helical molecules without stereogenic centers and with well-defined structure, strain, electronic properties and chirality are investigated by experimental and theoretical circular dichroism spectroscopy.
TL;DR: Lys73 and Lys79 are shown to replace Met80 as the axial ligand in the two conformers of state IV that were detected in previous studies, and the pKa for the conformational equilibrium between state III and state IV of the wild-type protein is found to be intermediate.
Abstract: The alkaline conformation (state IV) of yeast iso-1-ferricytochrome c and variants in which selected lysyl residues were replaced with alanyl residues has been studied by 1H NMR spectroscopy, electronic spectroscopy, EPR spectroscopy, direct electrochemistry, pH-jump kinetics, and temperature-dependent circular dichroism spectroscopy. On the basis of the NMR studies, Lys73 and Lys79 are shown to replace Met80 as the axial ligand in the two conformers of state IV that were detected in previous studies (Hong, X. L.; Dixon, D. W. FEBS Lett. 1989, 246, 105−108; Ferrer, J. C.; Guillemette, J. G.; Bogumil, R.; Inglis, S. C.; Smith, M.; Mauk, A. G. J. Am. Chem. Soc. 1993, 115, 7507−7508). The pKa for the conformational equilibrium between state III (native conformation) and state IV of the wild-type protein (8.70(2)) is found to be intermediate between that of the Lys73 bound conformer (8.44(1)) and that of the Lys79 bound conformer (8.82(2)) (0.1 M NaCl, 25 °C) as are the kinetic parameters for the conversion o...
TL;DR: In this article, stable state absorption and emission, circular dichroism (CD), and time-of-flight secondary-ion-mass-spectroscopic (TOF−SIMS) measurements were performed to study the complexation of tetracycline (TC) and anhydrotetracyCLine (AHTC) with Mg2+ and Ca2+ ions, respectively, in aqueous solutions at pH 8.02.
Abstract: Steady-state absorption and emission, circular dichroism (CD), and time-of-flight secondary-ion-mass-spectroscopic (TOF−SIMS) measurements were performed to study the complexation of tetracycline (TC) and anhydrotetracycline (AHTC) with Mg2+ and Ca2+ ions, respectively, in aqueous solutions at pH 8.02. The results obtained suggest that Ca2+ forms a 1:2 ligand:metal complex with TC via chelation through O10−O11 and O12−O1 and induces thereby the extended conformation A of TC, which is stabilized through hydrogen bonding between the deprotonated dimethylamino nitrogen, N4, and OH12a. pH titrations provide evidence that N4 deprotonates in the presence of a 164-fold molar excess of Ca2+ at approximately pH ⩾ 7.7 (cTC = 2.1 × 10-5 M). In contrast to Ca2+, Mg2+ binds to N4−O3 and thereby stabilizes the twisted conformation B of TC. TOF−SIMS measurements indicate that a 1:2 ligand:metal complex is formed in addition to the 1:1 complex. The Mg2+-induced increase in the fluorescence intensity and the observed chan...
TL;DR: In this article, a micro-scale method based on exciton-coupled CD which does not require chromophoric derivatizations is described, which can be extended to amino acids and amino alcohols after simple chemical modifications.
Abstract: We describe a microscale method based on exciton-coupled CD which does not require chromophoric derivatizations. The achiral chromophoric host porphyrin tweezer 1 binds to an acyclic chiral diamine through nitrogen/zinc coordination to form a macrocyclic host -guest complex; the CD of which reflects the absolute configuration of the diamine. This method can be extended to amino acids and amino alcohols after simple chemical modifications. The absolute configuration of amines has been determined by the exciton-coupled CD method, a microscale approach widely applied to a variety of compounds containing two or more chromophores. 1 This CD method results from through-space interaction of isolated chromophores which can be preexisting within the parent molecule or introduced by derivatization of -OH, -NH2, etc. Examples for its application in determining absolute configuration of amines include Schiff base formation with aromatic aldehyde chromophores, 2 quaternary ammonium salts of tertiary amines, 3 and intramolecular bisporphyrin chiral stacking induced by derivatized acyclic diamines with single stereogenic centers. 4 The absolute configuration of amines has also been investigated by the benzene chirality rule (sector rule) 5
TL;DR: Spectroscopic and kinetic data suggest that rhIFN-gamma aggregates through an intermediate form possessing a large amount of residual secondary structure, in contrast to the aggregates formed under denaturing stresses, the salted-out protein has a remarkably nativelike secondary structure.
TL;DR: It is found that oxidative modification of methionines in the carboxyl-terminal domain does not predispose CaM to further oxidative modification, and methionine oxidation results in no large-scale alterations in the tertiary structure of CaMox.
TL;DR: The voltage-dependent, anion-selective channel (VDAC) is generally considered the main pathway for metabolite diffusion across the mitochondrial outer membrane and it is proposed that the N-terminal domain normally resides in a groove in the lumen wall and that gating stimuli favor its displacement, destabilizing the putative beta-barrel.
TL;DR: The solution structure of Abeta(1-40)Met(O), the methionine-oxidized form of amyloid beta-peptide Abeta, has been investigated by CD and NMR spectroscopy and data show that oxidation inhibits a coil-to-beta-sheet transition in water.
Abstract: The solution structure of A beta(1-40)Met(O), the methionine-oxidized form of amyloid beta-peptide A beta(1-40), has been investigated by CD and NMR spectroscopy. Oxidation of Met35 may have implications in the aetiology of Alzheimer's disease. Circular dichroism experiments showed that whereas A beta(1-40) and A beta(1-40)Met(O) both adopt essentially random coil structures in water (pH 4) at micromolar concentrations, the former aggregates within several days while the latter is stable for at least 7 days under these conditions. This remarkable difference led us to determine the solution structure of A beta(1-40)Met(O) using H-1 NMR spectroscopy. In a water-SDS micelle medium needed to solubilize both peptides at the millimolar concentrations required to measure NMR spectra, chemical shift and NOE data for A beta(1-40)Met(O) strongly suggest the presence of a helical region between residues 16 and 24. This is supported by slow H-D exchange of amide protons in this region and by structure calculations using simulated annealing with the program XPLOR. The remainder of the structure is relatively disordered. Our previously reported NMR data for A beta(1-40) in the same solvent shows that helices are present over residues 15-24 (helix 1) and 28-36 (helix 2), Oxidation of Met35 thus causes a local and selective disruption of helix 2. In addition to this helix-coil rearrangement in aqueous micelles, the CD data show that oxidation inhibits a coil-to-beta-sheet transition in water. These significant structural rearrangements in the C-terminal region of A beta may be important clues to the chemistry and biology of A beta(1-40) and A beta(1-42).
TL;DR: It is suggested that in LH2 of Rb.
Abstract: In this paper, we report the circular dichroism (CD) spectra of two types of LH2-only mutants of Rhodobacter sphaeroides. In the first, only the wild type LH2 is present, while i the second, the B800 binding site of LH2 has been either destabilized or removed. For the first time, we have identified a band in the CD spectrum of LH2, located at approximately 780 nm, that can be ascribed to the high exciton component of the B850 band. The experimental spectra have been modeled by theoretical calculations. On this basis, the average interaction strength between the monomers in the B850 ring can be estimated to be approximately 300 cm-1. In addition, we suggest that in LH2 of Rb. sphaeroides the angles made by the Qy transitions of the B850 BChls with respect to the plane of the ring are slightly different from those calculated from the crystal structure of the Rhodopseudomonas acidophila LH2 complex.
TL;DR: Thermal denaturation of mouse monoclonal immunoglobulin G (isotype 1), as well as structural rearrangements resulting from adsorption on a hydrophobic Teflon surface, are studied by circular dichroism spectroscopy.
TL;DR: The attainment of a unique, native‐like state was achieved through the introduction of: helix capping interactions; electrostatic interactions between partially exposed charged residues; and a diverse collection of apolar side chains within the hydrophobic core.
Abstract: A monomolecular native-like three-helix bundle has been designed in an iterative process, beginning with a peptide that noncooperatively assembled into an antiparallel three-helix bundle. Three versions of the protein were designed in which specific interactions were incrementally added. The hydrodynamic and spectroscopic properties of the proteins were examined by size exclusion chromatography, sedimentation equilibrium, fluorescence spectroscopy, and NMR. The thermodynamics of folding were evaluated by monitoring the thermal and guanidine-induced unfolding transitions using far UV circular dichroism spectroscopy. The attainment of a unique, native-like state was achieved through the introduction of: (1) helix capping interactions; (2) electrostatic interactions between partially exposed charged residues; (3) a diverse collection of apolar side chains within the hydrophobic core.
TL;DR: Circular dichroism (CD) spectroscopy was used to understand more precisely the conformational aspects of the drug-membrane systems and it is noteworthy that C(13)-OH group, which strongly favours formation of the dimeric species in aqueous solutions when compared to idarubicin prevent association inside the LUV bilayer.
TL;DR: The discovery of two distinct states of PG-1 may correspond to the surface state and the insertion state of alamethicin, since they show a similar dependence on lipid composition, peptide concentration, and hydration condition.
Abstract: Protegrin-1 (PG-1), a β-sheet antimicrobial peptide, was studied in aligned lipid bilayers by oriented circular dichroism (OCD). All of its spectra measured in a variety of lipid compositions were linear superpositions of two primary basis spectra, indicating that PG-1 existed in two different states in membranes. We designated these as state S and state I. The state assumed by PG-1 was strongly influenced by lipid composition, peptide concentration, and hydration condition. We have previously reported that the helical peptides, alamethicin and magainin, also exhibit two distinct OCD basis spectraone corresponding to surface adsorption with the helix parallel to the bilayer and the other with perpendicular transbilayer insertion. States S and I of PG-1 may correspond to the surface state and the insertion state of alamethicin, since they show a similar dependence on lipid composition, peptide concentration, and hydration condition. Nonoriented CD spectra obtained from vesicle, micelle, and solution prepar...
TL;DR: In this paper, the electronic structures of perturbed blue copper proteins stellacyanin (STC) and cucumber basic protein (CBP) are defined relative to that of the well-understood “classic” site found in plastocyanin (PLC) by combining the results of low-temperature optical absorption, circular dichroism, with density functional calculations.
Abstract: The electronic structures of the perturbed blue copper proteins stellacyanin (STC) and cucumber basic protein (CBP, also called plantacyanin, PNC) are defined relative to that of the well-understood “classic” site found in plastocyanin (PLC) by combining the results of low-temperature optical absorption, circular dichroism, and magnetic circular dichroism spectra with density functional calculations. Additionally, absorption and magnetic circular dichroism spectra of Alcaligenes denitrificans wild-type and M121Q azurin are presented and compared to PLC and STC, respectively. These studies show that the principal electronic structure changes in CBP/PNC, with respect to PLC, are a small shift of the ligand field transitions to higher energy and a rotation of the Cu dx2-y2 half-filled HOMO which increases the pseudo-σ and decreases the π interactions of the cysteine (Cys) sulfur with Cu dx2-y2 and, in addition, mixes some methionine (Met) sulfur character into the HOMO. The geometrical distortion responsible...
TL;DR: These studies show that variations in the molecular structure of the diacetylenic phospholipid, lipid concentration, and solution conditions allow for control of the number of bilayers in the tubule walls, but not their diameter.
Abstract: Several techniques for controlling the morphology of self-assembled lipid tubules are investigated by using circular dichroism spectroscopy and electron microscopy. These studies show that variations in the molecular structure of the diacetylenic phospholipid, lipid concentration, and solution conditions allow for control of the number of bilayers in the tubule walls, but not their diameter. Tubules formed in water and mixtures of alcohols adopt interesting morphologies and allow for further control of tubule structure. In addition, studies of lipids with different acyl chains show that tubule morphology is sensitive to the degree of order within the chains. Because of the chiral molecular architecture in lipid tubules, intense peaks in their circular dichroism spectra are observed. These peaks can be monitored to obtain information on the tubule morphology. This information is correlated to direct observations made using electron microscopy. Results of these studies have led to the optimization of large ...