Tenascin-C-derived peptide TNIIIA2 highly enhances cell survival and platelet-derived growth factor (PDGF)-dependent cell proliferation through potentiated and sustained activation of integrin α5ß1.

Tenascin-C is an adhesion modulatory matrix protein that is highly expressed in tumors; however, its biochemical activity involved in tumorigenesis is not fully understood. On the other hand, increasing evidence indicates the importance of integrin α5ß1 in cancer development. We previously demonstrated that tenascin-C harbors a functional site that can be released as a proadhesive peptide such as TNIIIA2. Peptide TNIIIA2 is capable of inducing activation of ß1-integrins including α5ß1 via syndecan-4. In this study the proadhesive effect of TNIIIA2 was characterized by potentiated and sustained activation of integrin α5ß1. Based on this effect, TNIIIA2 rendered nontransformed fibroblasts (NIH3T3) resistant to serum deprivation-elicited anoikis through activation of the Akt/Bcl-2 pathway. Moreover, TNIIIA2 hyperstimulated PDGF-dependent proliferation of NIH3T3 by activating integrin α5ß1. Tenascin-C, a parental protein of TNIIIA2, also stimulated PDGF-dependent proliferation, which was blocked by a matrix metalloproteinase-2/9 inhibitor and an anti-TNIIIA2 function-blocking antibody, suggesting proteolytic exposure of the proadhesive effect of TNIIIA2. Mechanistic analyses revealed that TNIIIA2 induced a lateral association of PDGF receptor ß with the molecular complex of activated integrin α5ß1 and syndecan-4 in the membrane microdomains enriched with cholesterol/caveolin-1, resulting in prolonged activation of PDGF receptor ß and the subsequent Ras/mitogen-activated protein kinase pathway in a PDGF-dependent manner. Of note, TNIIIA2 induced continuous proliferation in NIH3T3 in an integrin α5ß1-dependent manner even after they formed a confluent monolayer. Thus, it was proposed that tenascin-C might be involved in deregulated cell growth through potentiated and sustained activation of integrin α5ß1 after exposure of the proadhesive effect of TNIIIA2.

Eukaryotic translation elongation factor 1A induces anoikis by triggering cell detachment.

Anoikis, apoptosis because of loss of cell anchorage, is crucial for tissue homeostasis. Fibronectin not only provides a scaffold for cell anchorage but also harbors a cryptic antiadhesive site capable of inducing ß1-integrin inactivation. In this study, this cryptic antiadhesive site is implicated in spontaneous induction of anoikis. Nontransformed fibroblasts (NIH3T3) adhering to a fibronectin substratum underwent anoikis during serum starvation culture. This anoikis was caused by proteolytic exposure of the cryptic antiadhesive site in fibronectin by matrix metalloproteinase. Eukaryotic elongation factor 1A (eEF1A) was identified as a membrane receptor for the exposed antiadhesive site. Serum starvation raised the membrane residence of eEF1A, and siRNA-based disruption of this increase rendered cells anoikis-resistant. By contrast, cells became more susceptible to anoikis in parallel with increased membrane residence of eEF1A by enforced expression. These results demonstrate that eEF1A acts as a membrane receptor for the cryptic antiadhesive site of fibronectin, which contributes to cell regulation, including anoikis, through negative regulation of cell anchorage.

Simultaneous enhancement of cell proliferation and thermally induced harvest efficiency based on temperature-responsive cationic copolymer-grafted microcarriers.

The development of large-scale suspension cell cultures using microcarriers has long been a focus of attention in the fields of pharmacy and biotechnology. Previously, we developed cell-detachable microcarriers based on temperature-responsive poly(N-isopropylacrylamide) (PIPAAm)-grafted beads, on which adhering cells can be noninvasively harvested by only reducing the temperature without the need for proteolytic enzyme treatment. In this study, to improve the cell harvest efficiency from bead surfaces while maintaining cell adhesion and proliferation properties, we prepared temperature-responsive cationic copolymer-grafted beads bearing a copolymer brush consisting of IPAAm, positively charged quaternary amine monomer (3-acrylamidopropyl trimethylammonium chloride; APTAC), and hydrophobic monomer (N-tert-butylacrylamide; tBAAm). The incorporation of positively charged APTAC into the grafted copolymer brush facilitated bead dispersibility in a cell culture system containing Chinese hamster ovary (CHO-K1) cells and consequently allowed for enhanced cell proliferation in the system compared to that of unmodified CMPS and conventional PIPAAm homopolymer-grafted beads. Additionally, P(IPAAm-co-APTAC-co-tBAAm) terpolymer-grafted beads exhibited the most rapid and efficient cell detachment behavior after the temperature was reduced to 20 °C, presumably because the highly hydrated APTAC promoted the overall hydration of the P(IPAAm-co-APTAC-co-tBAAm) chains. Therefore, P(IPAAm-co-APTAC-co-tBAAm) terpolymer-grafted microcarriers are effective in facilitating both cell proliferation and thermally induced cell detachment in a suspension culture system.

Synthesis of new UV-B light absorbents: (Acetylphenyl)glycosides with antioxidant activities.

m-Acetylphenyl-beta-d-glucopyranosides and m-acetylphenyl-alpha/beta-d-mannopyranosides were synthesized by the Koenigs-Knorr, Mitsunobu, and Helferich reactions as key glycosylation reactions, respectively. Their spectroscopic properties and antioxidative activities were characterized as potential ultraviolet B-ray absorbents.

The use of biotin-avidin binding to facilitate biomodification of thermoresponsive culture surfaces.

Here, we report biomodification of temperature-responsive culture surfaces with biotinylated biomolecules utilizing streptavidin and biotinylation of the surfaces. Poly(N-isopropylacrylamide-co-2-carboxyisopropylacrylamide) was covalently grafted onto tissue culture polystyrene (TCPS) dishes. Biotinylated Arg-Gly-Asp-Ser (RGDS) peptides with different spacer lengths (biotin-conjugated G(n)RGDS (n=1,6,12,16)) were examined. Human umbilical vein endothelial cells (HUVECs) adhered and were well spread on G(12)RGDS-immobilized surfaces in the absence of serum at 37 degrees C, while much less cell adhesion was observed with the other peptides. Adhered HUVECs were detached on reducing temperature to 20 degrees C, or on adding free RGDS peptide. Interestingly, cell detachment was accelerated by applying both these techniques. Consequently, by optimizing the spacer length, biomolecules can be functionally immobilized onto thermoresponsive surfaces via the affinity binding between avidin and biotin.

A fibronectin fragment induces tumor necrosis factor production of rat basophilic leukemia cells.

Proteolytic digest of fibronectin (FN), but not intact FN, induced TNF-alpha secretion of rat basophilic leukemia (RBL-2H3) cells. As a result of the identification of FN fragment responsible for TNF-alpha secretion, a 30-kDa fragment derived from the carboxyl-terminal heparin-binding (Hep 2) domain of FN was isolated from the FN digest. The TNF-alpha secretion was abrogated by treatment of RBL-2H3 cells with cycloheximide, indicating the de novo synthesis of TNF-alpha, but not with polymyxin B, excluding the possible TNF-alpha induction by some contaminated lipopolysaccharides. A 22-mer synthetic peptide originated from the Hep 2 domain, termed FNIII14, which has been found to negatively modulate the beta1 integrin activation, had the ability to induce TNF-alpha production, whereas this activity of FNIII14 disappeared by shuffling a YTIYVIAL sequence essential for the integrin-inactivating activity. FNIII14 suppressed the spreading of RBL-2H3 cells on FN substrate, wherein RBL-2H3 cell proliferation was inhibited with FNIII14 in a dose-dependent manner. Thus, it appears that FN fragments containing the YTIYVIAL anti-adhesive site affect the activation status of RBL-2H3 mast cells, characterized by the stimulation of TNF-alpha production and growth suppression, probably due to negative regulation of beta1 integrin activity.

Mechanochromic Dynamic Covalent Elastomers: Quantitative Stress Evaluation and Autonomous Recovery.

Stress evaluation in polymeric materials is important in order to not only spot danger in them before serious failure, but also precisely interpret the destructive mechanism, which can improve the lifetime and durability of polymeric materials. Here, we are able to visualize stress by color changes, as well as quantitatively estimate the stress in situ, in segmented polyurethane elastomers with diarylbibenzofuranone-based dynamic covalent mechanophores. We prepared films of the segmented polyurethanes, in which the mechanophores were incorporated in the soft segments, and efficiently activated them by mechanical force. Cleavage of the mechanophores during uniaxial elongation and their recovery after the removal of the stress were quantitatively evaluated by in situ electron paramagnetic resonance measurements, accompanied by drastic color changes.

Chemical modification of chitosan. Part 15: synthesis of novel chitosan derivatives by substitution of hydrophilic amine using N-carboxyethylchitosan ethyl ester as an intermediate.

The Michael type reaction of chitosan with ethyl acrylate has been investigated. Although this reaction was quite slow in the case of chitosan, the reiteration of the reaction was an effective means for increasing the degree of substitution (DS) of ethyl ester. The N-carboxyethylchitosan ethyl ester as an intermediate was successfully substituted with various hydrophilic amines, although the simultaneous hydrolysis of the ester to carboxylic acid also occurred. Water-soluble chitosan derivatives were obtained by substitution with hydroxyalkylamines and diamines.

Factors influencing the luminescence intensity of europium(III) complexes prepared via synergistic extraction.

The excitation and luminescence spectra of Eu(III) extracted with pivaloyltrifluoroacetone (HA) and/or 2,2'-bipyridyl (B) into CHCl3 were measured. The data were compared to those obtained in an HA/CHCl3 solution into which EuA3 or EuA3B was dissolved. The results are summarized as follows: (1) The degree of HA influence on the luminescence intensity differs in the two systems; in the HA/CHCl3-dissolved EuA3, the intensity abruptly decreases when the HA concentration exceeds approximately 10(-2)M, depending on EuA3 concentration. The data measuring the size of the dominant species in the CHCl3 containing EuA3 and HA via DLS indicate that the abrupt concentration quenching is due to the formation of aggregate consisting of EuA3 and HA. However, in the solvent-extracted sample, the luminescence intensity is not influenced by the HA concentration, even at 0.1M HA. This difference can be explained by the difference in water content. (2) In the synergistic extraction of Eu(III) with HA and B, the intensity is not substantially influenced by HA. The effect of HA on the luminescence intensity in the B/CHCl3-dissolved EuA3 is larger than that obtained via solvent extraction. These results suggest that synergistic extraction could be an efficient method for preparing the phosphor in solution and that, when using luminescence intensity to determine Eu(III) concentration, one should be careful for the other materials, such as HA, that are involved in the solution and serve as reference materials.

Molecular logistics using cytocleavable polyrotaxanes for the reactivation of enzymes delivered in living cells.

The intracellular delivery of enzymes is an essential methodology to extend their therapeutic application. Herein, we have developed dissociable supermolecule-enzyme polyelectrolyte complexes based on reduction-cleavable cationic polyrotaxanes (PRXs) for the reactivation of delivered enzymes. These PRXs are characterized by their supramolecular frameworks of a polymeric chain threading into cyclic molecules, which can form polyelectrolyte complexes with anionic enzymes while retaining their three dimensional structure, although their enzymatic activity is reduced. Upon the addition of a reductant, the PRXs dissociate into their constituent molecules and release the enzymes, resulting in a complete recovery of enzymatic activity. Under the intracellular environment, the PRX-based enzyme complexes showed the highest intracellular enzymatic activity and efficient activation of anticancer prodrugs to induce cytotoxic effects in comparison with the non-dissociable complexes and the commercial cell-penetrating peptide-based reagents. Thus, the intracellularly dissociable supermolecules are an attractive system for delivering therapeutic enzymes into living cells.

Novel method using hybrid markers: development of an approach for pulmonary measurement of multi-walled carbon nanotubes.

BACKGROUND: Multi-walled carbon nanotubes (MWCNT)s are suspected to induce pulmonary and pleural cancers due to their asbestos-like configurations. Therefore, accurate measurement of inhaled nanotubes in target organs is crucial for assessing cancer risk. Conventionally, nanotubes are measured after combustion at high temperature for conversion into CO2; however, the sensitivity is poor and the method lacks versatility. We have therefore developed a novel approach using hybrid markers for nanotube analysis, featuring high sensitivity and the capacity to conduct repeated analyses. The method involves adsorption of markers to nanotubes, followed by their desorption and assessment by means of high performance liquid chromatography (HPLC). METHODS: Recovery of MWCNT from rat lungs was conducted, and pulmonary MWCNT amounts were determined using rats intratracheally-exposed to MWCNT aerosol at 5 mg/m3 for 6 hours/day. RESULTS: The correlation coefficient for the calibration curve of MWCNT weight and the HPLC area was 0.9991. Consequently, the lower quantitation limit yielded was 0.2 µg. The recovery was 92-98% at approximately 0.4-2.0 µg demonstrating that MWCNTs in the lung could be measured accurately and precisely. CONCLUSIONS: We have developed a novel method using a hybrid marker approach for nanotube analysis, featuring very high sensitivity and the capacity to conduct repeated analyses. We further confirmed correlations between the amounts of nanotubes and markers and pulmonary nanotube measurement demonstrated that trace amounts could be detected with values closely relating to the administered dose, verifying that the method is sensitive and precise.

Selective separation of samarium(III) by synergistic extraction with ß-diketone and methylphenylphenanthroline carboxamide.

Synergistic extraction of trivalent lanthanides (Lns(III)) with pivaloyltrifluoroacetone (HA) and N-methyl-N-phenyl-1,10-phenanthroline-2-carboxamide (MePhPTA) was evaluated across the Ln series. The distribution ratio (D) of Sm(III) under an identical condition was the largest among all Lns(III). The separation factor (SF) between Sm(III) and Nd(III) (SF=D(Sm)/D(Nd)) was 2.0 and SF between Sm(III) and Eu(III), (D(Sm)/D(Eu)) was 1.4. Upon analyzing the extraction data in detail on the basis of mass balance, it was found that the dominant extracted species of light Lns(III) was a stable ternary complex consisting of Ln(III), HA, and MePhPTA (B), namely, LnA(3)B, while the dominant extracted species of heavy Lns(III) was the ion pair, [LnA(2)B](+)ClO(4)(-). The complex for Pr(III) was very stable (the stability constant, ߯, denoted as [LnA(3)B](o)[LnA(3)](o)(-1)[B](o)(-1), was 10(8.3)). It suggests that LnA(3) can form two 5-membered rings with MePhPTA, and the size of Pr(III) matches to the distance between the donor atoms in MePhPTA. Although the stability constant decreased with increasing Ln atomic number, the synergistic extraction constant (K(ex31)=[LnA(3)B](o)[H(+)](3)[Ln(3+)](-1)[HA](o)(-3)[B](o)(-1)) was the largest for Sm(III). Since the constant, K(ex31,) is given by K(ex31)=K(ex30)×߯ where K(ex30)=[LnA(3)](o)[H(+)](3)[Ln(3+)](-1)[HA](o)(-3), the largest K(ex31) of Sm(III) is attributable to the difference of the degree of the variation of K(ex30) between the light and the heavy Lns(III); the increment of extraction constant of LnA(3) (logK(ex30)) for light Lns is larger than the decrement of the stability constant of LnA(3)B (log߯), while the increment of logK(ex30) of post-Sm lessens than the decrement of log߯. From these results, it is concluded that selective separation of a particular Ln(III) among all Lns(III) is possible using synergistic extraction with a suitable combination of a multidentate ß-diketone and a Lewis base.

Effect of the polymer chain length of poly(N-isopropylacrylamide) on the temperature-responsive phase transition behavior of its conjugates with [60]fullerene.

In order to develop biomedical materials with specific functionalities, thermoresponsive conjugates [poly(N-isopropylacrylamide)-C(60) (PIPAAm-C(60)) ]of [60]fullerene (C(60)) and PIPAAm with two different polymer chain lengths (4 and 20 kDa) were synthesized by atom transfer radical polymerization. The effects of the polymer chain length on the temperature-responsive phase transition behavior of the synthetic PIPAAm-C(60) conjugates were probed by means of various physicochemical techniques. The coexistence of unimers and molecular assemblies of PIPAAm-C(60) was observed by gel permeation chromatography and dynamic light scattering studies in two PIPAAm-C(60) aqueous solutions below their lower critical solution temperatures (LCSTs). Additionally, below their LCSTs, differences in PIPAAm chain length gave rise to changes in the composition of the unimers and molecular assemblies. In response to temperature, the absorbance of the PIPAAm-C(60) aqueous solution changed according to a two-step behavior profile. Increasing temperature during the primary stage, where a change in the absorbance of the PIPAAm-C(60) aqueous solution took place, did not change the transition temperature, regardless of the solution concentration of PIPAAm-C(60). This absorbance change was associated with the phase transition of the molecular assemblies of PIPAAm-C(60). However, at the second stage, the transition temperature shifted to a higher value with the decrease in the concentration of PIPAAm-C(60), in the same manner as free PIPAAm chains. The second change was associated with the phase transition of the unimeric PIPAAm-C(60). Differences in PIPAAm chain length gave rise to the change in the phase transition behavior of PIPAAm-C(60) aqueous solution. Therefore, the chain length of PIPAAm was found to be a predominant factor involved in the solution characteristics of PIPAAm-C(60). Consequently, the PIPAAm-C(60) is expected to be an intelligent biomaterial possessing heat-induced accumulation and bioactivities.

Absence of binding between the human transferrin receptor and the transferrin complex of biological toxic trace element, aluminum, because of an incomplete open/closed form of the complex.

Human transferrin (Tf) very tightly binds two ferric ions to deliver iron to cells. Fe(III)(2)Tf (Fe(2)Tf) binds to the Tf receptor (TfR) at pH 7.4; however, iron-free Tf (apoTf) does not. Iron uptake is facilitated by endocytosis of the Fe(2)Tf-TfR complex. Tf can also bind aluminum ions, which cause toxic effects and are associated with many diseases. Since Al(III)(2)Tf (Al(2)Tf) does not bind to TfR, the uptake of aluminum by the cells does not occur through a TfR-mediated pathway. We have studied the absence of binding between Al(2)Tf and TfR by investigating the physicochemical characteristics of apoTf, Al(2)Tf, Fe(2)Tf, and TfR. The hydrodynamic radius of 38.8 A for Al(2)Tf obtained by dynamic light scattering was between that of 42.6 A for apoTf and 37.2 A for Fe(2)Tf. The zeta potential of -11.3 mV for Al(2)Tf measured by capillary electrophoresis was close to -11.2 mV for apoTf as compared to -11.9 mV for Fe(2)Tf, indicating that the Al(2)Tf surface had a relatively scarce negative charge as the apoTf surface had. These results demonstrated that the structure of Al(2)Tf was a trade-off between the closed and open forms of Fe(2)Tf and apoTf, respectively. Consequently, it is suggested that Al(2)Tf cannot form specific ionic interresidual interactions, such as those formed by Fe(2)Tf, to bind to TfR, resulting in impossible complex formation between Al(2)Tf and TfR.

Computational structure models of apo and diferric transferrin-transferrin receptor complexes.

Complexation of transferrin (Tf) and its receptor (TfR) is an essential event for iron uptake by the cell. Much data has been accumulated regarding Tf-TfR complexation, such as results from mutagenesis. We created 3D structural models of apo-human Tf-TfR (apoTf-TfR) and Fe(III)(2)Tf-TfR (Fe(2)Tf-TfR) complexes by computational rigid body refinement. The models are consistent with published mutagenesis experiments. In our models, the C-lobes of apoTf and Fe(2)Tf bind to the helical domain of TfR, and the N-lobes are sandwiched between the ectodomain of TfR and the cell membrane as previously reported. Further, the molecules of apoTf and Fe(2)Tf are not forced to undergo large conformational changes upon complexation. The creation of the models led a new and important finding that a residue of TfR, R651, which is called a hot spot for Tf-TfR binding, interacts with Tf E385 when either apoTf or Fe(2)Tf bind to TfR. The models rationally interpret the iron release from Fe(2)Tf-TfR upon acidification, dissociation of apoTf from TfR at slightly alkaline pH, and metal specific recognition of TfR.

Identification of an N-acetylcysteine conjugate in the urine after oral administration of 2,4-dichloro-1-nitrobenzene to rats.

Oral administration of 2,4-dichloro-1-nitrobenzene (2,4-DCNB) causes kidney tumors in the rat. The objective of the present study was to identify the chemical structure of 2,4-DCNB metabolites in urine. Urine from 2,4-DCNB fed rats was more yellow than urine from control rats, exhibiting a broad UV-spectrum around a peak wavelength of 360 nm; the control urine did not have an absorbance. The yellow component was extracted and analyzed. The optical properties of the yellow component were the same as the N-acetylcysteine conjugate of 1,4-dichloro-2-nitrobenzene (1,4-DCNB): 1,4-DCNB is secreted in urine as an N-acetylcysteine conjugate. LC-MS/MS analyses of this yellow component demonstrated its chemical structure to be the N-acetylcysteine conjugate of 2,4-DCNB. Nuclear overhauser effect and LC-MS/MS analyses revealed the structural isomer of this 2,4-DCNB metabolite as N-acetyl-S-(5-chloro-2-nitrophenyl)-L-cysteine. We also discuss the possibility that the N-acetylcysteine conjugate identified in this study plays a role as a proximate carcinogen in the formation of kidney tumors.

VLA-5-mediated adhesion to fibronectin accelerates hemin-stimulated erythroid differentiation of K562 cells through induction of VLA-4 expression.

Fibronectin plays important roles in erythropoiesis through the fibronectin receptors VLA-4 and VLA-5. However, the substantial role of these fibronectin receptors and their functional assignment in erythroid differentiation are not yet fully understood. Here, we investigated the effects of cell adhesion to fibronectin on erythroid differentiation using K562 human erythroid progenitor cells. Erythroid differentiation could be induced in K562 cells in suspension by stimulating with hemin. This hemin-stimulated erythroid differentiation was highly accelerated when cells were induced to adhere to fibronectin by treatment with TNIIIA2, a peptide derived from tenascin-C, which has recently been found to induce beta1-integrin activation. Another integrin activator, Mn(2+), also accelerated hemin-stimulated erythroid differentiation. Adhesive interaction with fibronectin via VLA-4 as well as VLA-5 was responsible for acceleration of the hemin-stimulated erythroid differentiation in response to TNIIIA2, although K562 cells should have been lacking in VLA-4. Adhesion to fibronectin forced by TNIIIA2 causally induced VLA-4 expression in K562 cells, and this was blocked by the RGD peptide, an antagonist for VLA-5. The resulting adhesive interaction with fibronectin via VLA-4 strongly enhanced the hemin-stimulated activation of p38 mitogen-activated protein kinase, which was shown to serve as a signaling molecule crucial for erythroid differentiation. Suppression of VLA-4 expression by RNA interference abrogated acceleration of hemin-stimulated erythroid differentiation in response to TNIIIA2. Thus, VLA-4 and VLA-5 may contribute to erythropoiesis at different stages of erythroid differentiation.

Biological selection of peptides for poly(l-lactide) substrates.

Short peptides that recognize the alpha form of poly( l-lactide) (PLLA) crystalline films were identified from a phage-displayed peptide library. An enzyme-linked immunosorbent assay (ELISA) revealed that the apparent binding constants of the phage clones for the alpha form of PLLA were greater than those of the unselected phage library. The specificity index for the alpha form of PLLA referred to a structurally similar atactic poly(methyl methacrylate) (at-PMMA), supporting the alpha form of PLLA specific binding of the selected phage. Amino acid residues with proton-donor lateral groups and hydrophobic alkyl groups were relatively enriched in a sequence of heptapeptides on the specific phage clones, thereby suggesting the presence of hydrogen bonding as well as hydrophobic interactions between the alpha form of PLLA and the peptides. Surface plasmon resonance (SPR) analysis revealed that the binding constant of the freed c22 heptapeptide (Gln-Leu-Met-His-Asp-Tyr-Arg) for the alpha form of PLLA was greater than those for reference at-PMMA, amorphous PLLA, and the beta form of PLLA. It was found that c22 peptide can recognize slight differences in PLLA polymorphs such as a crystalline state and an arrangement of PLLA functional groups.

Antiadhesive sites present in the fibronectin type III-like repeats of human plasma fibronectin.

We have found that fibronectin (FN) has a functional cryptic site opposing cell adhesion to extracellular matrix (ECM): a synthetic FN peptide derived from the 14th FN type III-like (FN-III) repeat, termed peptide FNIII14, inhibits cell adhesion to the FN without binding to beta1 integrins. This antiadhesive activity of peptide FNIII14 depends on its C-terminal amino acid sequence YTIYVIAL. A 50-kDa membrane protein (p50) has been detected as a specific binding protein of peptide FNIII14. Here we showed that antiadhesive activity of peptide FNIII14 was depedent upon the presence of p50 on cell surfaces. Furthermore, we found that there exists a sequence, analogous to the YTIYVIAL, in the 10th FN-III repeat of the FN molecule and that a FN peptide containing this analogous sequence, termed peptide FNIII10, inhibited cell adhesion to the FN. Peptide FNIII10 appeared to share p50 with peptide FNIII14 in expressing the antiadhesive activity. As a physiological consequence of decreased adhesion, peptides FNIII10 and FNIII14 accelerated the anoikis-like apoptosis of normal fibroblasts by down-regulating Bcl-2 expression through blocking the FAK/PI3K/Akt signaling pathway. Thus, the YTIYVIAL-related sequences of the FN molecule may be involved in cell regulation by modulating negatively cell adhesion to the ECM, in which p50 probably serves as a membrane receptor.

Thermally induced coil-to-helix transition of sodium gellan gum with different molar masses in aqueous salt solutions.

Using 5 samples of well-purified Na-gellans (Na-gellans G1-G5, weight-average molar mass M(w) = 120 x 10(3)-32 x 10(3) at 40 degrees C), the effects of molar mass on the coil-to-double-helix transition in aqueous solutions with 25 mM NaCl were studied by light scattering and circular dichroism (CD) measurements, viscometry, and differential scanning calorimetry (DSC). From the temperature dependence of M(w), molar ellipticity at 201 nm [theta]201, intrinsic viscosity [eta], and DSC exothermic curves, it was found that the coil-to-double-helix transitions for G1-G5 samples took place at almost the same temperature. The [eta] and M(w) obtained in the temperature range from 40 to 25 degrees C can be explained by a simple coil/double-helix equilibrium model using the double-helix contents determined from CD data. The van't Hoff's transition enthalpy deltaH(vH) of Na-gellans depended on M(w). It is concluded that the coil-to-double-helix transitions of Na-gellans are all-or-none type transitions, and are accelerated with increasing M(w).