Triple Helix

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Barbara Brodsky - One of the best experts on this subject based on the ideXlab platform.

  • location of glycine mutations within a bacterial collagen protein affects degree of disruption of Triple Helix folding and conformation
    Journal of Biological Chemistry, 2011
    Co-Authors: Haiming Cheng, Shayan Rashid, Zhuoxin Yu, Ayumi Yoshizumi, Eileen S Hwang, Barbara Brodsky
    Abstract:

    The hereditary bone disorder osteogenesis imperfecta is often caused by missense mutations in type I collagen that change one Gly residue to a larger residue and that break the typical (Gly-Xaa-Yaa)n sequence pattern. Site-directed mutagenesis in a recombinant bacterial collagen system was used to explore the effects of the Gly mutation position and of the identity of the residue replacing Gly in a homogeneous collagen molecular population. Homotrimeric bacterial collagen proteins with a Gly-to-Arg or Gly-to-Ser replacement formed stable Triple-Helix molecules with a reproducible 2 °C decrease in stability. All Gly replacements led to a significant delay in Triple-Helix folding, but a more dramatic delay was observed when the mutation was located near the N terminus of the Triple-Helix domain. This highly disruptive mutation, close to the globular N-terminal trimerization domain where folding is initiated, is likely to interfere with Triple-Helix nucleation. A positional effect of mutations was also suggested by trypsin sensitivity for a Gly-to-Arg replacement close to the Triple-Helix N terminus but not for the same replacement near the center of the molecule. The significant impact of the location of a mutation on Triple-Helix folding and conformation could relate to the severe consequences of mutations located near the C terminus of type I and type III collagens, where trimerization occurs and Triple-Helix folding is initiated.

  • mechanism of stabilization of a bacterial collagen Triple Helix in the absence of hydroxyproline
    Journal of Biological Chemistry, 2007
    Co-Authors: Angela Mohs, Teresita Silva, Takeshi Yoshida, Ravish Amin, Slawomir Lukomski, Masayori Inouye, Barbara Brodsky
    Abstract:

    Abstract The Streptococcus pyogenes cell-surface protein Scl2 contains a globular N-terminal domain and a collagen-like domain, (Gly-Xaa-X′aa)79, which forms a Triple Helix with a thermal stability close to that seen for mammalian collagens. Hyp is a major contributor to Triple-Helix stability in animal collagens, but is not present in bacteria, which lack prolyl hydroxylase. To explore the basis of bacterial collagen Triple-Helix stability in the absence of Hyp, biophysical studies were carried out on recombinant Scl2 protein, the isolated collagen-like domain from Scl2, and a set of peptides modeling the Scl2 highly charged repetitive (Gly-Xaa-X′aa)n sequences. At pH 7, CD spectroscopy, dynamic light scattering, and differential scanning calorimetry of the Scl2 protein all showed a very sharp thermal transition near 36 °C, indicating a highly cooperative unfolding of both the globular and Triple-Helix domains. The collagen-like domain isolated by trypsin digestion showed a sharp transition at the same temperature, with an enthalpy of 12.5 kJ/mol of tripeptide. At low pH, Scl2 and its isolated collagen-like domain showed substantial destabilization from the neutral pH value, with two thermal transitions at 24 and 27 °C. A similar destabilization at low pH was seen for Scl2 charged model peptides, and the degree of destabilization was consistent with the strong pH dependence arising from the GKD tripeptide unit. The Scl2 protein contained twice as much charge as human fibril-forming collagens, and the degree of electrostatic stabilization observed for Scl2 was similar to the contribution Hyp makes to the stability of mammalian collagens. The high enthalpic contribution to the stability of the Scl2 collagenous domain supports the presence of a hydration network in the absence of Hyp.

  • electrostatic interactions involving lysine make major contributions to collagen Triple Helix stability
    Biochemistry, 2005
    Co-Authors: Anton V Persikov, John A M Ramshaw, And Alan Kirkpatrick, Barbara Brodsky
    Abstract:

    Important stabilizing features for the collagen Triple Helix include the presence of Gly as every third residue, a high content of imino acids, and interchain hydrogen bonds. Host-guest peptides have been used previously to characterize Triple-Helix propensities of individual residues and Gly-X-Y Triplets. Here, comparison of the thermal stabilities of host-guest peptides of the form (Gly-Pro-Hyp)3-Gly-X-Y-Gly-X'-Y'-(Gly-Pro-Hyp)3 extends the study to adjacent tripeptide sequences, to encompass the major classes of potential direct intramolecular interactions. Favorable hydrophobic interactions were observed, as well as stabilizing intrachain interactions between residues of opposite charge in the i and i + 3 positions. However, the greatest gain in Triple-Helix stability was achieved in the presence of Gly-Pro-Lys-Gly-Asp/Glu-Hyp sequences, leading to a T(m) value equal to that seen for a Gly-Pro-Hyp-Gly-Pro-Hyp sequence. This stabilization is seen for Lys but not for Arg and can be assigned to interchain ion pairs, as shown by molecular modeling. Computational analysis shows that Lys-Gly-Asp/Glu sequences are present at a frequency much greater than expected in collagen, suggesting this interaction is biologically important. These results add significantly to the understanding of which surface ion pairs can contribute to protein stability.

  • molecular structure of the collagen Triple Helix
    Advances in Protein Chemistry, 2005
    Co-Authors: Barbara Brodsky, Anton V Persikov
    Abstract:

    Abstract The molecular conformation of the collagen Triple Helix confers strict amino acid sequence constraints, requiring a (Gly-X-Y)n repeating pattern and a high content of imino acids. The increasing family of collagens and proteins with collagenous domains shows the collagen Triple Helix to be a basic motif adaptable to a range of proteins and functions. Its rodlike domain has the potential for various modes of self-association and the capacity to bind receptors, other proteins, GAGs, and nucleic acids. High-resolution crystal structures obtained for collagen model peptides confirm the supercoiled Triple Helix conformation, and provide new information on hydrogen bonding patterns, hydration, sidechain interactions, and ligand binding. For several peptides, the Helix twist was found to be sequence dependent, and such variation in Helix twist may serve as recognition features or to orient the Triple Helix for binding. Mutations in the collagen Triple-Helix domain lead to a variety of human disorders. The most common mutations are single-base substitutions that lead to the replacement of one Gly residue, breaking the Gly-X-Y repeating pattern. A single Gly substitution destabilizes the Triple Helix through a local disruption in hydrogen bonding and produces a discontinuity in the register of the Helix. Molecular information about the collagen Triple Helix and the effect of mutations will lead to a better understanding of function and pathology.

  • peptide investigations of pairwise interactions in the collagen Triple Helix
    Journal of Molecular Biology, 2002
    Co-Authors: Anton V Persikov, John A M Ramshaw, Alan Kirkpatrick, Barbara Brodsky
    Abstract:

    Pairwise interactions have been studied for the major secondary structures in proteins. The present work extends the characterization of interactions between side-chains to the context of a collagen Triple-Helix. In this study, the most frequent Gly-X-Y tripeptide sequences in collagen are characterized in terms of interchain interactions between non-imino acid X and Y residues, through the use of host-guest peptides and statistical frequency analysis. Stabilities predicted on the basis of additivity show good agreement with experimental values for almost half of the peptides, indicating a lack of interaction. A small number of peptides have a stability lower than predicted, while a larger number are more stable than expected. Of all Triplets containing residues of opposite charge, only Gly-Lys-Asp and Gly-Arg-Asp exhibit stabilizing electrostatic interactions, and these pairs are found together preferentially in collagens. Repulsion of like charges is observed in Gly-Arg-Lys, Gly-Lys-Arg, and Gly-Glu-Asp sequences, and a small degree of hydrophobic stabilization was observed for the Gly-Leu-Leu guest Triplet. The data reported here help clarify basic principles of Triple-Helix stability. In addition, the experimentally determined stabilities of the tripeptide units found most frequently in collagens constitute a database useful for predicting Triple-Helix stability in peptides, collagens and other Triple-Helix-containing proteins.

Robert R Jacobs - One of the best experts on this subject based on the ideXlab platform.

  • partially opened Triple Helix is the biologically active conformation of 1 3 β glucans that induces pulmonary inflammation in rats
    Journal of Toxicology and Environmental Health, 2003
    Co-Authors: Shihhoung Young, Victor A Robinson, Mark Barger, David G Frazer, Vincent Castranova, Robert R Jacobs
    Abstract:

    1 M 3- g -Glucans produce pulmonary inflammation in rats and are commonly found in indoor air dust samples. Conformation is an important factor determining the biological activity of 1 M 3- g -glucans. The partially opened Triple-Helix conformation induced by NaOH treatment and the annealed Triple-Helix conformation have been identified by fluorescence resonance energy transfer spectroscopy in our previous study. The objective of this study was to examine the role of these conformations of 1 M 3- g -glucans in the induction of pulmonary inflammation in rats. A partially opened Triple-Helix conformation of the known inflammatory 1 M 3- g -glucan zymosan was prepared by treating zymosan with NaOH followed by neutralization and dialysis. The annealed Triple-Helix conformation was prepared by allowing the partially opened Triple-Helix conformation to anneal for 9 d at room temperature. Rats were exposed to fresh or annealed NaOH-treated zymosan via intratracheal instillation. The results show that the zymosan...

  • observation of a partially opened Triple Helix conformation in 1 3 β glucan by fluorescence resonance energy transfer spectroscopy
    Journal of Biological Chemistry, 2000
    Co-Authors: Shihhoung Young, Wenji Dong, Robert R Jacobs
    Abstract:

    Abstract This study used fluorescence resonance energy transfer (FRET) spectroscopy as an indirect method to investigate the effect of NaOH treatment on the conformation of a Triple-Helix (1→3)-β-d-glucan and then evaluated the effect of conformation on biological activity. Previous studies have suggested that treatment of the Triple-Helix glucans with NaOH produces single-Helix conformers. FRET spectra of the Triple-Helix glucan, laminarin, doubly labeled with 1-aminopyrene as donor probe and fluorescein-5-isothiocyanate as acceptor probe attached at the reducing end, showed that a partially opened Triple-Helix conformer was formed on treatment with NaOH. Increasing degrees of strand opening was associated with increasing concentrations of NaOH. Based on these observations we propose that a partially opened Triple-Helix rather than a single Helix, is formed by treating the Triple-Helix glucans with NaOH. After neutralizing the NaOH, changes in FRET indicated that the partially opened conformer gradually reverts to the Triple-Helix over 8 days. Laminarian was stabilized at different degrees of partial opening and its biological activity examined using theLimulus amebocyte lysate assay and nitric oxide production by alveolar macrophage. Both Limulus amebocyte lysate activity and nitric oxide production were related to the degree of opening of the Triple-Helix. Partially open conformers were more biologically active than the intact Triple-Helix.

Loet Leydesdorff - One of the best experts on this subject based on the ideXlab platform.

  • the Triple Helix in the context of global change dynamics and challenges
    Prometheus, 2014
    Co-Authors: Lawton H Smith, Loet Leydesdorff
    Abstract:

    Understanding how economies change through interactions with science and government as different spheres of activity requires both new conceptual tools and methodologies. In this paper, the evolution of the metaphor of a Triple Helix of university–industry–government relations is elaborated into an evolutionary model, and positioned within the context of global economic changes. We highlight how Triple Helix relations are both continuing and mutating, and the conditions under which a Triple Helix might be seen to be unraveling in the face of pressures on each of the three helices – university, industry, and government. The reciprocal dynamics of innovation both in the Triple Helix thesis and in the global economy are empirically explored: we find that footlooseness of high technology manufacturing and knowledge-intensive services counteract the embeddedness prevailing in medium technology manufacturing. The geographical level at which synergy in Triple Helix relations can be expected and sustained varies among nations and regions.

  • can synergy in Triple Helix relations be quantified a review of the development of the Triple Helix indicator
    Triple Helix, 2014
    Co-Authors: Loet Leydesdorff, Han Woo Park
    Abstract:

    Triple Helix arrangements of bi- and trilateral relations can be considered as adaptive ecosystems. During the last decade, we have further developed a Triple Helix indicator of synergy as reduction of uncertainty in niches that can be shaped among three or more sets of relations. Reduction of uncertainty can be generated in correlations among distributions of relations, but this (next-order) effect can be considered as a feedback counterbalancing the uncertainty generated in the localized relations. We first explain the indicator and then review possible results when this indicator is applied to (i) co-author networks of academic, industrial, and governmental authors and (ii) synergies in the distributions of firms over geographical addresses, technological classes, and industrial-size classes for a number of nations. Co-variation is then considered as a measure of relationship. The balance between globalizing and localizing dynamics can be quantified. Too much synergy locally can also be considered as lock-in. Tendencies are different for the globalizing knowledge dynamics versus locally retaining wealth from knowledge in industrial innovations.

  • a routine for measuring synergy in university industry government relations mutual information as a Triple Helix and quadruple Helix indicator
    Scientometrics, 2014
    Co-Authors: Loet Leydesdorff, Han Woo Park, Balazs Lengyel
    Abstract:

    Mutual information in three (or more) dimensions can be considered as a Triple-Helix indicator of possible synergy in university---industry---government relations. An open-source routine th4.exe makes the computation of this indicator interactively available at the internet, and thus applicable to large sets of data. Th4.exe computes all probabilistic entropies and mutual information in two, three, and, if available in the data, four dimensions among, for example, classes such as geographical addresses (cities, regions), technological codes (e.g. OECD's NACE codes), and size categories; or, alternatively, among institutional addresses (academic, industrial, public sector) in document sets. The relations between the Triple-Helix indicator--as an indicator of synergy--and the Triple-Helix model that specifies the possibility of feedback by an overlay of communications, are also discussed.

  • can synergy in Triple Helix relations be quantified a review of the development of the Triple Helix indicator
    arXiv: Computers and Society, 2014
    Co-Authors: Loet Leydesdorff, Han Woo Park
    Abstract:

    Triple-Helix arrangements of bi- and trilateral relations can be considered as adaptive eco-systems. During the last decade, we have further developed a Triple-Helix indicator of synergy as reduction of uncertainty in niches that can be shaped among three or more distributions. Reduction of uncertainty can be generated in correlations among distributions of relations, but this (next-order) effect can be counterbalanced by uncertainty generated in the relations. We first explain the indicator, and then review possible results when this indicator is applied to (i) co-author networks of academic, industrial, and governmental authors and (ii) synergies in the distributions of firms over geographical addresses, technological classes, and industrial-size classes for a number of nations. Co-variation is then considered as a measure of relationship. The balance between globalizing and localizing dynamics can be quantified. Too much synergy locally can also be considered as lock-in. Tendencies are different for the globalizing knowledge dynamics versus locally retaining wealth from knowledge in industrial innovations.

  • a routine for measuring synergy in university industry government relations mutual information as a Triple Helix and quadruple Helix indicator
    arXiv: Computers and Society, 2012
    Co-Authors: Loet Leydesdorff, Han Woo Park, Balazs Lengyel
    Abstract:

    Mutual information in three (or more) dimensions can be considered as a Triple-Helix indicator of synergy in university-industry-government relations. An open-source routine th4.exe makes the computation of this indicator interactively available at the Internet, and thus applicable to large sets of data. Th4.exe computes all probabilistic entropies and mutual information in two, three, and, if available in the data, four dimensions among, for example, classes such as geographical addresses (cities, regions), technological codes (e.g., OECD's NACE codes), and size categories; or, alternatively, among institutional addresses (academic, industrial, public sector) in document sets. The relations between the Triple-Helix indicator -- as an indicator of synergy -- and the Triple-Helix model that specifies the possibility of feedback by an overlay of communications, are also discussed.

John A M Ramshaw - One of the best experts on this subject based on the ideXlab platform.

  • electrostatic interactions involving lysine make major contributions to collagen Triple Helix stability
    Biochemistry, 2005
    Co-Authors: Anton V Persikov, John A M Ramshaw, And Alan Kirkpatrick, Barbara Brodsky
    Abstract:

    Important stabilizing features for the collagen Triple Helix include the presence of Gly as every third residue, a high content of imino acids, and interchain hydrogen bonds. Host-guest peptides have been used previously to characterize Triple-Helix propensities of individual residues and Gly-X-Y Triplets. Here, comparison of the thermal stabilities of host-guest peptides of the form (Gly-Pro-Hyp)3-Gly-X-Y-Gly-X'-Y'-(Gly-Pro-Hyp)3 extends the study to adjacent tripeptide sequences, to encompass the major classes of potential direct intramolecular interactions. Favorable hydrophobic interactions were observed, as well as stabilizing intrachain interactions between residues of opposite charge in the i and i + 3 positions. However, the greatest gain in Triple-Helix stability was achieved in the presence of Gly-Pro-Lys-Gly-Asp/Glu-Hyp sequences, leading to a T(m) value equal to that seen for a Gly-Pro-Hyp-Gly-Pro-Hyp sequence. This stabilization is seen for Lys but not for Arg and can be assigned to interchain ion pairs, as shown by molecular modeling. Computational analysis shows that Lys-Gly-Asp/Glu sequences are present at a frequency much greater than expected in collagen, suggesting this interaction is biologically important. These results add significantly to the understanding of which surface ion pairs can contribute to protein stability.

  • peptide investigations of pairwise interactions in the collagen Triple Helix
    Journal of Molecular Biology, 2002
    Co-Authors: Anton V Persikov, John A M Ramshaw, Alan Kirkpatrick, Barbara Brodsky
    Abstract:

    Pairwise interactions have been studied for the major secondary structures in proteins. The present work extends the characterization of interactions between side-chains to the context of a collagen Triple-Helix. In this study, the most frequent Gly-X-Y tripeptide sequences in collagen are characterized in terms of interchain interactions between non-imino acid X and Y residues, through the use of host-guest peptides and statistical frequency analysis. Stabilities predicted on the basis of additivity show good agreement with experimental values for almost half of the peptides, indicating a lack of interaction. A small number of peptides have a stability lower than predicted, while a larger number are more stable than expected. Of all Triplets containing residues of opposite charge, only Gly-Lys-Asp and Gly-Arg-Asp exhibit stabilizing electrostatic interactions, and these pairs are found together preferentially in collagens. Repulsion of like charges is observed in Gly-Arg-Lys, Gly-Lys-Arg, and Gly-Glu-Asp sequences, and a small degree of hydrophobic stabilization was observed for the Gly-Leu-Leu guest Triplet. The data reported here help clarify basic principles of Triple-Helix stability. In addition, the experimentally determined stabilities of the tripeptide units found most frequently in collagens constitute a database useful for predicting Triple-Helix stability in peptides, collagens and other Triple-Helix-containing proteins.

  • collagen model peptides sequence dependence of Triple Helix stability
    Biopolymers, 2000
    Co-Authors: Anton V Persikov, John A M Ramshaw, Barbara Brodsky
    Abstract:

    The Triple Helix is a specialized protein motif, found in all collagens as well as in noncollagenous proteins involved in host defense. Peptides will adopt a Triple-helical conformation if the sequence contains its characteristic features of Gly as every third residue and a high content of Pro and Hyp residues. Such model peptides have proved amenable to structural studies by x-ray crystallography and NMR spectroscopy, suitable for thermodynamic and kinetic analysis, and a valuable tool in characterizing the binding activities of the collagen Triple Helix. A systematic approach to understanding the amino acid sequence dependence of the collagen Triple Helix has been initiated, based on a set of host-guest peptides of the form, (Gly-Pro-Hyp)(3)-Gly-X-Y-(Gly-Pro-Hyp)(4). Comparison of their thermal stabilities has led to a propensity scale for the X and Y positions, and the additivity of contributions of individual residues is now under investigation. The local and global stability of the collagen Triple Helix is normally modulated by the residues in the X and Y positions, with every third position occupied by Gly in fibril-forming collagens. However, in collagen diseases, such as osteogenesis imperfecta, a single Gly may be substituted by another residue. Host-guest studies where the Gly is replaced by various amino acids suggest that the identity of the residue in the Gly position affects the degree of destabilization and the clinical severity of the disease.

  • positional preferences of ionizable residues in gly x y Triplets of the collagen Triple Helix
    Journal of Biological Chemistry, 1997
    Co-Authors: Virginia C Chan, Konrad Beck, John A M Ramshaw, Alan Kirkpatrick, Barbara Brodsky
    Abstract:

    Collagens contain a high amount of charged residues involved in Triple-Helix stability, fibril formation, and ligand binding. The contribution of charged residues to stability was analyzed utilizing a host-guest peptide system with a single Gly-X-Y Triplet embedded within Ac(Gly-Pro-Hyp)3-Gly-X-Y-(Gly-Pro-Hyp)4-Gly-Gly-NH2. The ionizable residues Arg, Lys, Glu, and Asp were incorporated into the X position of Gly-X-Hyp; in the Y position of Gly-Pro-Y; or as pairs of oppositely charged residues occupying X and Y positions. The Gly-X-Hyp peptides had similar thermal stabilities, only marginally less stable than Gly-Pro-Hyp, whereas Gly-Pro-Y peptides showed a wide thermal stability range (Tm = 30-45 degrees C). The stability of peptides with oppositely charged residues in the X and Y positions appears to reflect simple additivity of the individual residues, except when X is occupied by a basic residue and Y = Asp. The side chains of Glu, Lys, and Arg have the potential to form hydrogen bonds with available peptide backbone carbonyl groups within the Triple-Helix, whereas the shorter Asp side chain does not. This may relate to the unique involvement of Asp residues in energetically favorable ion pair formation. These studies clarify the dependence of Triple-Helix stability on the identity, position, and ionization state of charged residues.

  • gly pro arg confers stability similar to gly pro hyp in the collagen Triple Helix of host guest peptides
    Journal of Biological Chemistry, 1997
    Co-Authors: Wei Yang, Alan Kirkpatrick, John A M Ramshaw, Virginia C Chan, Barbara Brodsky
    Abstract:

    A set of host-guest peptides of the form Ac(Gly-Pro-Hyp)3-Gly-X-Y-(Gly-Pro-Hyp)4-Gly-Gly-NH2has been designed to evaluate the propensity of different Gly-X-Y Triplets for the Triple-Helix conformation (Shah, N. K., Ramshaw, J. A. M., Kirkpatrick, A., Shah, C., and Brodsky, B. (1996)Biochemistry 35, 10262–10268). All Gly-X-Y guest Triplets led to a decrease in melting temperature from the host (Gly-Pro-Hyp)8 peptide except for Gly-Pro-Arg. In this Gly-Pro-Hyp-rich environment, Gly-Pro-Arg was found to be as stabilizing as Gly-Pro-Hyp. Decreased stability of host-guest peptides containing Gly-Pro-Lys, Gly-Pro-homo-Arg, and Gly-Arg-Hyp compared with Gly-Pro-Arg indicated a stabilization that is optimal for Arg and specific to theY-position. Arg was found to have a similar stabilizing effect when residues other than Pro are in the X-position. Both Arg and Hyp stabilize the Triple-Helix preferentially in theY-position in a stereospecific manner and occupy largelyY-positions in collagen. However, contiguous Gly-Pro-Hyp units are highly stable and promote Triple-Helix folding, whereas incorporation of multiple Gly-Pro-Arg Triplets was destabilizing and folded slowly due to charge repulsion. In collagen, Gly-Pro-Arg may contribute maximally to local Triple-Helix stability while also having the potential for electrostatic interactions in fibril formation and binding.

Shihhoung Young - One of the best experts on this subject based on the ideXlab platform.

  • partially opened Triple Helix is the biologically active conformation of 1 3 β glucans that induces pulmonary inflammation in rats
    Journal of Toxicology and Environmental Health, 2003
    Co-Authors: Shihhoung Young, Victor A Robinson, Mark Barger, David G Frazer, Vincent Castranova, Robert R Jacobs
    Abstract:

    1 M 3- g -Glucans produce pulmonary inflammation in rats and are commonly found in indoor air dust samples. Conformation is an important factor determining the biological activity of 1 M 3- g -glucans. The partially opened Triple-Helix conformation induced by NaOH treatment and the annealed Triple-Helix conformation have been identified by fluorescence resonance energy transfer spectroscopy in our previous study. The objective of this study was to examine the role of these conformations of 1 M 3- g -glucans in the induction of pulmonary inflammation in rats. A partially opened Triple-Helix conformation of the known inflammatory 1 M 3- g -glucan zymosan was prepared by treating zymosan with NaOH followed by neutralization and dialysis. The annealed Triple-Helix conformation was prepared by allowing the partially opened Triple-Helix conformation to anneal for 9 d at room temperature. Rats were exposed to fresh or annealed NaOH-treated zymosan via intratracheal instillation. The results show that the zymosan...

  • observation of a partially opened Triple Helix conformation in 1 3 β glucan by fluorescence resonance energy transfer spectroscopy
    Journal of Biological Chemistry, 2000
    Co-Authors: Shihhoung Young, Wenji Dong, Robert R Jacobs
    Abstract:

    Abstract This study used fluorescence resonance energy transfer (FRET) spectroscopy as an indirect method to investigate the effect of NaOH treatment on the conformation of a Triple-Helix (1→3)-β-d-glucan and then evaluated the effect of conformation on biological activity. Previous studies have suggested that treatment of the Triple-Helix glucans with NaOH produces single-Helix conformers. FRET spectra of the Triple-Helix glucan, laminarin, doubly labeled with 1-aminopyrene as donor probe and fluorescein-5-isothiocyanate as acceptor probe attached at the reducing end, showed that a partially opened Triple-Helix conformer was formed on treatment with NaOH. Increasing degrees of strand opening was associated with increasing concentrations of NaOH. Based on these observations we propose that a partially opened Triple-Helix rather than a single Helix, is formed by treating the Triple-Helix glucans with NaOH. After neutralizing the NaOH, changes in FRET indicated that the partially opened conformer gradually reverts to the Triple-Helix over 8 days. Laminarian was stabilized at different degrees of partial opening and its biological activity examined using theLimulus amebocyte lysate assay and nitric oxide production by alveolar macrophage. Both Limulus amebocyte lysate activity and nitric oxide production were related to the degree of opening of the Triple-Helix. Partially open conformers were more biologically active than the intact Triple-Helix.