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At least 469 records · Page 26Linked to original sources
PubMed2006

Electrostatic interactions in the denatured state and in the transition state for protein folding: effects of denatured state interactions on the analysis of transition state structure.

The development of electrostatic interactions during the folding of the N-terminal domain of the ribosomal protein L9 (NTL9) is investigated by pH-dependent rate equilibrium free energy relationships. We show that Asp8, among six acidic residues, is involved in non-native, electrostatic interactions with K12 in the transition state for folding as well as in the denatured state. The perturbed native state pK(a) of D8 (pK(a) = 3.0) appears to be maintained through non-native interactions in both the transition state and the denatured state. Mutational effects on the stability of the transition state for protein (un)folding are often analyzed in respect to change in ground states. Thus, the interpretation of transition state analysis critically depends on an understanding of mutational effects on both the native and denatured state. Increasing evidence for structurally biased denatured states under physiological conditions raises concerns about possible denatured state effects on folding studies. We show that the structural interpretation of transition state analysis can be altered dramatically by denatured state effects.

Hydrogen-Ion Concentration↗
PubMed2006

The unified hypothesis of interactions among the bone, adipose and vascular systems: 'osteo-lipo-vascular interactions'.

Epidemiological evidence has established a link among hyperlipidemia, visceral obesity, osteoporosis, and cardiovascular diseases (CVD). We here propose the hypothesis that the associations of those disorders are based on interaction of the three organs, i.e. the bone, adipose, and vascular tissues, possibly through multiple interactions among several humoral factors and/or transcription factors. The unified hypothesis of three organs, which we call 'osteo-lipo-vascular interactions', may be explained by the common origin of the cells in each organ. The mesenchymal stem cells are capable of differentiating into osteoblasts, vascular smooth muscle cells, and adipocytes. Alternatively, macrophages may evolve into osteoclasts or infiltrate both the vascular and adipose tissues, thereby leading to chronic inflammation. This unified concept of three organs may provide insights into the development of a new drug for the treatment of osteoporosis, obesity, hyperlipidemia or CVD.

Adipose Tissue↗
PubMed2003

Calbindin D28K interacts with Ran-binding protein M: identification of interacting domains by NMR spectroscopy.

Calbindin D(28K) is an EF-hand containing protein that plays a vital role in neurological function. We now show that calcium-loaded calbindin D(28K) interacts with Ran-binding protein M, a protein known to play a role in microtubule function. Using NMR methods, we show that a peptide, LASIKNR, derived from Ran-binding protein M, interacts with several regions of the calcium-loaded protein including the amino terminus and two other regions that exhibit conformational exchange on the NMR timescale. We suggest that the interaction between calbindin D(28K) and Ran-binding protein M may be important in calbindin D(28K) function.

Adaptor Proteins, Signal Transducing↗
PubMed2003

The viral death protein Apoptin interacts with Hippi, the protein interactor of Huntingtin-interacting protein 1.

Apoptin, a chicken anemia virus-encoded protein, induces apoptosis in human tumor cells but not in normal cells. The tumor-specific activity of Apoptin is correlated with its nuclear localization in tumor cells. In an attempt to elucidate the molecular mechanism of Apoptin-induced apoptosis, we identified human Hippi, the protein interactor and apoptosis co-mediator of Huntingtin interacting protein 1, as one of the Apoptin-associated proteins by yeast two-hybrid screen. We also demonstrated that Hippi could interact with Apoptin both in vitro and in human cells. Furthermore, subcellular localization studies showed that Hippi and Apoptin perfectly colocalized in the cytoplasm of normal human HEL cells, whereas in cancerous HeLa cells most Apoptin and Hippi were located separately in the nucleus and cytoplasm and, thus, showed only a modest colocalization. Mapping studies indicate that Hippi binds within the self-multimerization domain of Apoptin, and Apoptin binds to the C-terminal half of Hippi, including its death effector domain-like motif. Our results suggest that the Apoptin-Hippi interaction may play a role in the suppression of apoptosis in normal cells.

Adaptor Proteins, Signal Transducing↗
PubMed1983

The stacking interactions in 7-methylguanine-tryptophan systems, a model study for the interaction between the 'cap' structure of mRNA and its binding protein.

Stacking interactions were shown by spectroscopic and X-ray crystallographic studies to be formed between the tryptophan and the protonated 7-methylguanine derivatives. These interactions would be in part responsible for the specific interaction between the 5'-terminal capped structure of mRNA and its binding protein.

Carrier Proteins↗
PubMed1976

Protein-metal ion interaction: volume effects produced by the interaction of proteins with metal ions.

The interaction of metal cations with single chain globular proteins produces volume increases, the magnitude of which is determined primarily by the ion and to a lesser extent by the protein. The cations are listed in ascending order of volume change: K(I) less than Mg(II) less than Sr(II) less than Ca(II) less than Co(II) less than Ni(II) less than Cd(II) less than Zn(II) less than Cu(II) less than Pb(II). This sequence held for all cation-protein systems investigated except for Cd(II) which produced a slightly larger volume effect than Zn(II) with lysozyme. The volume changes attributed to protein-cation interaction are positive and range from 8 ml/10(5) g of protein for the reaction on 0.05 M KNO3 with bovine plasma albumin to 2320 ml/10(5) g of protein produced by the 0.20 M Pb(NO3)2-myoglobin system. A similar classification scheme was not possible for the proteins. For example, volume increases of 45, 50, 80 and 95 ml/10(5) g of protein were produced when 0.05 M Mg(II) reacted with bovine serum albumin, ovalbumin, sperm whale myoglobin and lysozyme, respectively. However, when 0.2 M Pb(II) was the reactant the values were 1930, 846, 2320, and 1120 ml/10(5) g of protein. Volume effects produced by Cr(III), Al(III) and Fe(III) were determined, but the calculated results are considered dubious because the volume changes are a complicated function of protein-cation and protein-proton interaction.

Cations↗
PubMed2002

Nature of Interaction between basic fibroblast growth factor and the antiangiogenic drug 7,7-(carbonyl-bis[imino-N-methyl-4,2-pyrrolecarbonylimino[N-methyl-4,2-pyrrole]-carbonylimino])-bis-(1,3-naphtalene disulfonate). II. Removal of polar interactions affects protein folding.

Fibroblast growth factor-2 (basic FGF), a potent inducer of angiogenesis, and the naphthalene sulfonic distamycin A derivative, 7,7-(carbonyl-bis[imino-N-methyl-4,2-pyrrolecarbonylimino[N-methyl-4,2-pyrrole]-carbonylimino])-bis-(1,3-naphtalene disulfonate) (PNU145156E), which exhibits in vivo antiangiogenic activity, form a tight reversible (1:1) complex. PNU145156E binds to the heparin and the selenate-binding sites on bFGF. The cis bFGF-heparin (2:1) complex, essential for the activation of the angiogenic process, is thus prevented. The nature of the forces involved in bFGF:PNU145156E complex, using the wild-type and the K128Q, K138Q, K134Q, and K128Q-K138Q point mutated bFGFs was sought. Based on thermodynamic analysis of the complexation constants, protein temperature stability profiles by ultraviolet absorption, circular dichroism measurements, fluorescence Förster energy-transfer, and anisotropy studies, in harmony with the published x-ray crystallographic structure, the following molecular interactions are proposed: reduced coulombic interactions, hence loosening of the complex by the removal of charged polar groups from the bFGF-heparin binding cleft resulted in decreased binding constants and in a change in the binding mode from polar to nonpolar. Concomitantly, upon mutation, the protein was rendered more compact, less flexible, and less aqueously exposed compared with the wild type. These were further pronounced with the double mutant: weaker dominantly nonpolar protein-drug interactions were accompanied by conspicuous folding. With heparin, however, wild-type bFGF forms a tighter complex with a more compact structure.

Amino Acid Substitution↗
PubMed1990

Electron paramagnetic resonance investigation of photosynthetic reaction centers from Rhodobacter sphaeroides R-26 in which Fe2+ was replaced by Cu2+. Determination of hyperfine interactions and exchange and dipole-dipole interactions between Cu2+ and QA-.

We report electron paramagnetic resonance (EPR) experiments in frozen solutions of unreduced and reduced photosynthetic reaction centers (RCs) from Rhodobacter sphaeroides R-26 in which Fe2+ has been chemically replaced by the isotope 65Cu2+. Samples in which the primary quinone acceptor QA is unreduced (Cu2+QA:RCs) give a powder EPR spectrum typical for Cu2+ having axial symmetry, corresponding to a d(x2 - y2) ground state orbital, with g values g parallel = 2.314 +/- 0.001 and g perpendicular = 2.060 +/- 0.003. The spectrum shows a hyperfine structure for the nuclear spin of copper (65I = 3/2) with A parallel = (-167 +/- 1) x 10(-4) cm-1 and /A perpendicular/ = (16 +/- 2) x 10(-4) cm-1, and hyperfine couplings with three nitrogen ligands. This has been verified in samples containing the naturally occurring 14N isotope (l = 1), and in samples where the nitrogen ligands to copper were replaced by the isotope 15N (l = 1/2). We introduce a model for the electronic structure at the position of the metal ion which reflects the recently determined three-dimensional structure of the RCs of Rb. sphaeroides (Allen, J. P., G. Feher, T. O. Yeates, H. Komiya, and D. C. Rees. 1987. Proc. Natl. Acad. Sci. USA. 84:5730: Allen, J. P., G. Feher, T. O. Yeates, H. Komiya, and D. C. Rees. 1988. Proc. Natl. Acad. Sci. USA, 85:8487) as well as our EPR results. In this model the copper ion is octahedrally coordinated to three nitrogens from histidine residues and to one carboxylate oxygen from a glutamic acid, forming a distorted square in the plane of the d(x2 = y2) ground state orbital. It is also bound to a nitrogen of another histidine and to the other carboxylate oxygen of the same glutamic acid residue, in a direction approximately normal to this plane. The EPR spectrum changes drastically when the quinone acceptor QA is chemically reduced (Cu2+QA-:RCs); the change is due to the exchange and dipole-dipole interactions between the Cu2+ and QA- spins. A model spin Hamiltonian proposed for this exchange coupled cooper-quinone spin dimer accounts well for the observed spectra. From a comparison of the EPR spectra of the Cu2+QA:RC and CU2+QA-:RC complexes we obtain the values /J0/ = (0.30 +/- 0.02) K for the isotropic exchange coupling, and /d/ = (0.010 +/- 0.002) K for the projection of the dipole-dipole interaction tensor on the symmetry axis of the copper spin. From the EPR experiments only the relative signs of J0 and d can be deduced; it was determined that they have the same sign. The magnitude of the exchange coupling calculated for Cu2+QA-:RC is similar to that observed for the Fe2+QA-:RC complex (J0 = -0.43K). The exchange coupling is discussed in terms of the superexchange paths connecting the Cu2+ ion and the quinone radical using the structural data for the RCs of Rb. sphaeroides. From the value of the dipole-dipole interaction, d, we determined R approximately 8.4 A for the weighted distance between the metal ion and the quinone in reduced RCs, which is to be compared with 10 A obtained from x-ray analysis of unreduced RCs. This points to a shortening of the Cu2+ -QA- distance upon reduction of the quinone, as has been proposed by Allen et al. (1988).

Amino Acid Sequence↗
PubMed1991

Dipole interactions in electrofusion. Contributions of membrane potential and effective dipole interaction pressures.

The contributions of pulse-induced dipole-dipole interaction to the total pressure acting normal to the membranes of closely positioned pronase treated human erythrocytes during electrofusion was calculated. The total pressure was modeled as the sum of pressures arising from membrane potential and dipole-dipole attraction opposed by interbilayer repulsion. The dipole-dipole interaction was derived from the experimentally obtained cell polarizability. The threshold electric field amplitude necessary for fusion of pronase-treated human erythrocytes was experimentally obtained at various combinations of pulse duration, frequency, and the conductivity of the external medium. The theoretical values of the critical electric field amplitude compared favorably to the experimentally obtained threshold field amplitudes. Fusion by dc pulses may be primarily attributed to attainment of sufficiently high membrane potentials. However, with decreasing external conductivity and increasing sinusoidal pulse frequency (100 kHz-2.5 MHz), the induced dipole-dipole interactions provide the principal driving force for membrane failure leading to fusion.

Electric Stimulation↗
PubMed2000

Pair-wise interactions by gas chromatography. VII. Interaction free enthalpies of solutes with secondary alcohol groups.

A polar type liquid having a secondary alcohol substituent on a branched alkane skeleton, SOH, was used as stationary phase. The molecules of this stationary phase are nearly isomorphous and isochor with those of the branched alkane, C78, elected as standard, i.e., the molecules of both solvents have nearly the same form and the same size. Partition properties of 158 chosen molecular probes were measured by gas chromatography on SOH and on an SOH-C78 mixture having a volume fraction of thetaOH = 0.5. Based on the resulting data an interaction free enthalpy could be calculated, i.e., the additional effect of the secondary alcohol to partition. Comparison with data determined earlier on another member of this solvent family, POH, having a primary alcohol as interacting group gives information about the effect of steric hindrance on polar type solute-solvent interaction free energies.

Alcohols↗
PubMed2001

Structural determinants outside the PXDLS sequence affect the interaction of adenovirus E1A, C-terminal interacting protein and Drosophila repressors with C-terminal binding protein.

C-Terminal binding protein (CtBP) interacts with a highly conserved amino acid motif (PXDLS) at the C terminus of adenovirus early region 1A (AdE1A) protein. This amino acid sequence has recently been demonstrated in the mammalian protein C-terminal interacting protein (CtIP) and a number of Drosophila repressors including Snail, Knirps and Hairy. In the study described here we have examined the structures of synthetic peptides identical to the CtBP binding sites on these proteins using NMR spectroscopy. It has been shown that peptides identical to the CtBP binding site in CtIP and at the N terminus of Snail form a series of beta-turns similar to those seen in AdE1A. The PXDLS motif towards the C terminus of Snail forms an alpha-helix. However, the motifs in Knirps and Hairy did not adopt well-defined structures in TFE/water mixtures as shown by the absence of medium range NOEs and a high proportion of signal overlap. The affinities of peptides for Drosophila and mammalian CtBP were compared using enzyme-linked immunosorbent assay. CtIP, Snail (N-terminal peptide) and Knirps peptides all bind to mammalian CtBP with high affinity (K(i) of 1.04, 1.34 and 0.52 microM, respectively). However, different effects were observed with dCtBP, most notably the affinity for the Snail (N-terminal peptide) and Knirps peptides were markedly reduced (K(i) of 332 and 56 microM, respectively) whilst the Hairy peptide bound much more strongly (K(i) for dCtBP of 6.22 compared to 133 microM for hCtBP). In addition we have shown that peptides containing identical PXDLS motifs but with different N and C terminal sequences have appreciably different affinities for mammalian CtBP and different structures in solution. We conclude that the factors governing the interactions of CtBPs with partner proteins are more complex than simple possession of the PXDLS motif. In particular the overall secondary structures and amino acid side chains in the binding sites of partner proteins are of importance as well as possible global structural effects in both members of the complex. These data are considered evidence for a multiplicity of CtBPs and partner proteins in the cell.

Adenovirus E1A Proteins↗
PubMedDate not supplied

Molecular interaction studies of hemostasis: fibrinogen ligand-human platelet receptor interactions.

The interactions between fibrinogen ligands and platelet receptor alpha(IIb)beta(3) were studied under physiological conditions by atomic force microscopy (AFM). Two linear peptide sequences in fibrinogen, RGD and HHLGGAKQAGDV, play central roles in the regulation of hemostasis and thrombosis by facilitating adhesion and aggregation of platelets. In order to measure the interactions (i.e., debonding force), oligopeptides, GSSSGaaa, where aaa is -RGDSPA or -HHLGGAKQAGDV, were synthesized and grafted on to the surface of AFM probe tips. The interaction forces between a peptide-modified AFM probe tip and platelet surface were determined from pN to nN levels using AFM force measurements. Our results show that the zero kinetic off-rate, K(off)(0), for RGDSPA is significantly smaller than that for HHLGGAKQAGDV, under the consideration of flexible receptor surfaces. From our analysis, the K(off)(0), the single molecular binding energy E(b), and the transition state x(b), were extracted from the data, and estimated to be 1.53s(-1), -2.64x10(-20)J and 1.03A for the RGD-alpha(IIb)beta(3) system, and 47.58s(-1), 2.67x10(-20), 1.09A for the HHLGGAKQAGDV-alpha(IIb)beta(3) system, respectively.

Amino Acid Sequence↗
PubMed2004

Regulation of the insulin receptor by protein kinase C isoenzymes: preferential interaction with beta isoenzymes and interaction with the catalytic domain of betaII.

We analysed the effects of high glucose in rat1 cells overexpressing insulin receptor. High (25 mM) glucose inhibited insulin-stimulated tyrosine kinase activity completely at insulin concentrations of 1 and 5 ng/ml. Decapeptides modelled on insulin receptor sequences surrounding serines 1035 and 1270 were found to inhibit protein kinase C activity in vitro and after microinjection into cells blocked the inhibition of mitogenesis induced by glucose. Purification of receptor from 3T3L1 adipocytes revealed that only the isoenzymes beta1, betaII and delta were detected. The site of the interaction was mapped to the catalytic domain of betaII. These results demonstrate that the inhibition of insulin receptor tyrosine kinase activity can be ameliorated using insulin receptor peptide sequences and there is constitutive and differential interaction of individual PKC isoenzymes with the insulin receptor, and in the case of betaII, this interaction maps to the catalytic domain rather than the regulatory domain.

Animals↗
PubMed1999

A double interaction screen identifies positive and negative ftz gene regulators and ftz-interacting proteins.

Regulatory genes directing embryonic development are expressed in complex patterns. The Drosophila homeobox gene fushi tarazu (ftz) is expressed in a striped pattern that is controlled by several discrete and large cis- regulatory elements. One key cis-element is the ftz proximal enhancer which is required for stripe establishment and which mediates autoregulation by direct binding of Ftz protein. To identify the trans-acting factors that regulate ftz expression and autoregulation, we developed a modified yeast two hybrid screen, the Double Interaction Screen (DIS). The DIS was designed to isolate both DNA binding transcriptional regulators that interact with the proximal enhancer and proteins that interact with Ftz itself when it is bound to the enhancer. The screen identified two candidate Ftz protein cofactors as well as activators and repressors of ftz transcription that bind directly to the enhancer. One of these (Tramtrack (Ttk)) was previously shown to bind to at least five sites in the proximal enhancer; genetic studies suggested that Ttk acts as a repressor of ftz in the embryo. Here we show that, in yeast cells, Ttk protein strongly activates transcription, suggesting that yeast may be missing a necessary co-repressor which is present in Drosophila embryos. Further, we have characterized the activity of a second candidate ftz repressor isolated in the screen - the product of the pair-rule gene sloppy paired - a member of the forkhead family. We show that Slp1 is a DNA binding protein. We have identified a high affinity binding site for Slp1 in the ftz proximal enhancer. Slp1 represses transcription via this binding site in yeast cells, consistent with its role as a direct repressor of ftz stripes in interstripe regions during late stages of embryogenesis. The DIS should be a generally useful method to identify DNA binding transcriptional regulators and protein partners of previously characterized DNA binding proteins.

Animals↗
PubMed2003

Small interacting peptides. Part I. Interaction of cyclohexapeptides with an unspecific SiOH surface: comparison of infrared investigations and force field calculations.

The interaction of cyclohexapeptides c(X(1)(1)K(2)X(2)(3)K(4)X(3)(5)K(6)) in water with hydrolysed silicon surfaces were studied by attenuated total reflection Fourier transform infrared (ATR FTIR) spectroscopy and by force field calculations. The band sequences (1800-1500 cm(-1)) for dissolved and adsorbed cyclohexapeptides were recorded and compared with those obtained after flushing with distilled water in order to eliminate the background signal of the peptides in solution. Band analyses and principal component analyses were carried out for the characteristic peptide vibrations in order to evaluate the spectra. In addition, force field calculations were performed to study the binding energies to the surface and to illustrate the possible structures of the cyclohexapeptides. The positively charged lysine side chains of the cyclohexapeptides interact with the OH groups of the surface, as indicated by band shifts. This also was verified by the force field calculations. The bonding stability increases with the number of interacting sites (lysine side chains and other peptide residues) to the surface. These sites are determined by structure and polarity of the cyclohexapeptides.

Binding Sites↗
PubMed1999

Interaction of chemically modified antisense oligonucleotides with sense DNA: a label-free interaction study with reflectometric interference spectroscopy.

Antisense oligonucleotides (ON) are regarded as potential therapeutic agents for controlling gene expression at the mRNA level. The strength of the interaction with the target sequence is one critical factor for the therapeutic efficiency of an ON. Herein, the results of studies on antisense 15mer and 20mer ONs against mdr1b-mRNA are described. The mdr1b is a member of the group that encodes the P-glycoprotein (Pgp), responsible for the phenomenon of multidrug resistance. The effects of backbone modification (DNA, phosphorothioate (PTO)), terminal modifications (hexadecyl, cholesteryl, tocopherol, polyethylenglycol, 2'-O-methyl-modified RNA) and base sequence misalignments (1 to 3 bases) on interaction kinetics and binding strength were investigated. The interaction of an immobilized sense strand with the dissolved antisense ON was monitored with a label-free optical transducer based on thin film interference (RIfS). Association kinetics were detected at a low density of immobilized ON. Thermodynamics were investigated by homogeneous phase titration of sense and antisense ON and subsequent quantification of equilibrium concentrations of unbound ON at a transducer highly loaded with sense ON. Association rate constants varied from 3.1 (+/- 0.2) x 10(4) M-1 s-1 (poly(ethylene glycol)-modified DNA strand) to 4.3 (+/- 0.1) x 10(4) M-1 s-1 (hexadecyl-modified strand). Binding constants varied from 1.9 (+/- 0.1) x 10(8) M-1 (cholesteryl modification) to 5 (+/- 0.4) x 10(7) M-1 (tocopherol modification). Phosphorothioate ON showed a reduction in binding strength of more than 1 order of magnitude. The data presented give valuable information for the efficiency of modified antisense oligonucleotides.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Immobilized proteoliposome affinity chromatography for quantitative analysis of specific interactions between solutes and membrane proteins. Interaction of cytochalasin B and D-glucose with the glucose transporter Glut1.

An affinity gel bed was prepared by reconstitution of a transmembrane protein, the human red cell glucose transporter (Glut1), followed by steric immobilization of the proteoliposomes in small and rigid gel beads by freeze-thawing. The specific interactions between the reconstituted Glut1, the transport inhibitor cytochalasin B (CB), and the transported solute D-glucose were analyzed by isocratic chromatography of CB on the Glut1-proteoliposome gel bed. Specific retardation of CB which decreased upon inclusion of the competitor D-glucose in the eluent was observed on-line. The equilibrium constants for CB and D-glucose interaction with Glut1 (Kd 1.5 x 10(-7) M and 67 mM, respectively) obtained by use of equations derived for the affinity chromatographic analysis were consistent with values obtained by others by conventional methods. Effects of liposome composition, pH, and time on the CB binding activity of Glut1 were studied. Reconstitution of a membrane protein into a lipid environment and steric immobilization of the proteoliposomes favor retention of the protein activity. Immobilized proteoliposome affinity chromatography (IPAC) is a novel, powerful method for analysis of interactions between membrane proteins and solutes.

Chromatography, Affinity↗
PubMed1985

Role of peptide structure in lipid-peptide interactions: high-sensitivity differential scanning calorimetry and electron spin resonance studies of the structural properties of dimyristoylphosphatidylcholine membranes interacting with pentagastrin-related pentapeptides.

The effects of amino acid substitutions in the pentapeptide pentagastrin on the nature of its interactions with dimyristoylphosphatidylcholine (DMPC) are assessed by differential scanning calorimetry and electron spin resonance. In two peptide analogues, the Asp at position 4 in pentagastrin (N-t-Boc-beta-Ala-Trp-Met-Asp-Phe-NH2) is replaced by Gly or Phe. These uncharged, more hydrophobic peptides have little effect on the transition temperature of DMPC, but they broaden the transition and lower the transition enthalpy as do integral membrane proteins. These peptides also mimic the behavior of integral membrane proteins in decreasing the order of a 5-doxylstearic acid spin probe below the transition temperature and in exhibiting a second immobilized lipid component using a 16-doxylstearic acid spin probe in DMPC. Three charged peptides were studied: pentagastrin, an analogue with positions 4 and 5 reversed (i.e., ending in Phe-Asp-NH2), and one with Asp replaced by Arg at position 4. All three of these charged peptides altered the phase transition behavior of DMPC to give two components, one above and one below the transition temperature of the pure lipid. With increasing peptide concentration, the higher melting transition became more prominent. The arginine-containing peptide produced the largest shifts in melting temperature followed by pentagastrin and then the "reversed" peptide. The arginine-containing peptide also increased the enthalpy of the transition. These peptides also increased the ordering of DMPC below the phase transition as measured with both 5- and 16-doxylstearic acid. The ordering effect was most pronounced with the arginine-containing peptide using the 5-doxylstearic acid probe. The results demonstrate that even the zwitterionic DMPC can interact more strongly with positively charged peptides than with negatively charged ones. In addition, peptide sequence as well as composition is important in determining the nature of peptide-lipid interactions. The markedly different effects of these pentagastrin peptides on the phase transition and motional properties of DMPC occur despite the similar depth of burial of these peptides with DMPC.

Calorimetry, Differential Scanning↗