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PubMed2001

Modifying the temporal profile of the high-potency sweetener neotame.

It is possible, using hydrophobic organic acids (such as cinnamate) or hydroxyamino acids (such as serine and tyrosine), to modify the temporal profile of the high-potency sweetener neotame. On the basis of Monte Carlo simulations, it was concluded that it is unlikely that this effect is due to direct interaction between the neotame molecule and the taste modifier. It is shown, using conformational analysis and molecular modeling, that the taste modifiers can adopt low-energy conformers which mimic the proposed active conformation of neotame, which suggests that the modifiers may compete for binding at the receptor site.

Cinnamates↗
PubMed2005

Linolenic acid-modified chitosan for formation of self-assembled nanoparticles.

Chitosan was modified by coupling with linolenic acid through the 1-ethyl-3-(3-dimethylaminopropyyl)carbodiimide-mediated reaction. The degree of substitution was measured by 1H NMR, and it was 1.8%, i.e., 1.8 linolenic acids group per 100 anhydroglucose units. The critical aggregation concentration (CAC) of the self-aggregate of hydrophobically modified chitosan was determined by measuring the fluorescence intensity of the pyrene as a fluorescent probe. The CAC value in phosphate-buffered saline (PBS) solution (pH 7.4) was 5 x 10(-2) mg/mL. The average particle size of self-aggregates of hydrophobically modified chitosan in PBS solution (pH 7.4) was 210.8 nm with a unimodal size distribution ranging from 100 to 500 nm. A transmission electron microscopy study showed that the formation of near spherical shape nanoparticles had enough structural integrity. The loading ability of hydrophobically modified chitosan (LA-chitosan) was investigated by using bovine serum albumin (BSA) as a model protein. Self-aggregated nanoparticles exhibited an increased loading capacity (19.85 +/- 0.04 to 37.57 +/- 0.25%) with an increasing concentration of BSA (0.1-0.5 mg/mL).

Chitosan↗
PubMed1997

Synthesis and antiviral activity of certain 5'-modified analogs of 2,5,6-trichloro-1-(beta-D-ribofuranosyl)benzimidazole.

A series of 5'-modified 2,5,6-trichlorobenzimidazole ribonucleosides has been synthesized and tested for activity against two human herpesviruses and for cytotoxicity. The 5'-methoxy, 5'-ethoxy, and 5'-butoxy analogs of 2,5,6-trichloro-1-(beta-D-ribofuranosyl)benzimidazole (TCRB) were prepared by coupling the appropriate 5-O-alkyl-1,2,3-tri-O-acetyl-beta-D-ribose derivatives with 2,5,6-trichlorobenzimidazole followed by removal of the protecting groups. The 5'-deoxy-5'-fluoro, -5'-chloro, -5'-bromo, -5'-iodo, -5'-azido, and -5'-thiomethyl derivatives were synthesized in a similar fashion. All of these 5'-modified derivatives had significant activity against HCMV in plaque and yield reduction assays (IC50's = 0.5-14.2 microM) but had little activity (IC50's > 100 microM) against HSV-1. This pattern in similar to the antiviral activity profile observed for TCRB. The 5'-halogenated derivatives were more active than the other 5'-modified derivatives with antiviral activity well separated from cytotoxicity. In general, cytotoxicity of all the 5'-modified derivatives was greater in human foreskin fibroblasts (HFF cells) than in L1210 or KB tumor cells. These results indicate that the viral target tolerates significant modifications of TCRB at the 5'-position without adversely affecting activity against HCMV, whereas the 5'-modifications increased cytotoxicity in human diploid cells.

Animals↗
PubMed2006

Toward amide-modified RNA: synthesis of 3'-aminomethyl-5'-carboxy-3',5'-dideoxy nucleosides.

Recent discovery of RNA interference has reinvigorated the interest in chemically modified RNA. Chemical approaches may be used to optimize properties of small interfering RNAs, such as thermal stability, cellular delivery, in vivo half-life, and pharmacokinetics. From this perspective, amides as neutral and hydrophobic internucleoside linkages in RNA are highly interesting modifications that so far have not been tested in RNA interference. Amides are remarkably good mimics of the phosphodiester backbone of RNA and can be prepared using a relatively straightforward peptide coupling chemistry. The synthetic challenge that has hampered the progress in this field has been preparation of monomeric building blocks for such couplings, the nucleoside amino acid equivalents. Herein, we report two synthetic routes to enantiomerically pure 3'-aminomethyl-5'-carboxy-3',5'-dideoxy nucleosides, monomers for preparation of amide-modified RNA. Modification of uridine, a representative of natural nucleosides, using nitroaldol chemistry gives the target amino acid in 16 steps and 9% overall yield. The alternative synthesis starting from glucose is somewhat less efficient (17 steps and 6% yield of 3'-azidomethyl-5'-carboxy-3',5'-dideoxy uridine), but provides easier access to modified nucleosides having other heterocyclic bases. The syntheses developed herein will allow preparation of amide-modified RNA analogues and exploration of their potential as tools and probes for RNA interference, fundamental biochemistry, and bio- and nanotechnology.

Amides↗
PubMed2005

Characterization of ESR active species on lithium chloride-modified mesoporous silica.

The surface of mesoporous silica with regular nanometer-sized pores and high surface area has been modified by metal ions or functional groups to introduce specific interactions. We found that ESR active species were formed on lithium chloride (LiCl)-modified mesoporous silica after heat treatment. The structure and the surface properties of LiCl-modified mesoporous silica were characterized by XRD, ESR, nitrogen adsorption, UV-vis-NIR, and TPD. The results suggest that the ESR active species were generated on the surface in response to heat treatment above 673 K. Moreover, it was found for the first time that LiCl-modified mesoporous silica after the heat treatment has reversible adsorption properties for hydrogen under room temperature and atmospheric pressure.

Journal Article↗
PubMed2005

Pair correlation functions and the self-diffusion coefficient of Lennard-Jones liquid in the modified free volume theory of diffusion.

In this paper, we apply the Matteoli-Mansoori empirical formula for the pair correlation function of simple fluids obeying the Lennard-Jones potential to calculate reduced self-diffusion coefficients on the basis of the modified free volume theory. The self-diffusion coefficient thus computed as functions of temperature and density is compared with the molecular dynamics simulation data and the self-diffusion coefficient obtained by the modified free volume theory implemented with the Monte Carlo simulation method for the pair correlation function. We show that the Matteoli-Mansoori empirical formula yields sufficiently accurate self-diffusion coefficients in the supercritical regime, provided that the minimum free volume activating diffusion is estimated with the classical turning point of binary collision at the mean relative kinetic energy 3k(B)T/2, where k(B) is the Boltzmann constant and T is the temperature. In the subcritical regime, the empirical formula yields qualitatively correct, but lower values for the self-diffusion coefficients compared with computer simulation values and those from the modified free volume theory implemented with the Monte Carlo simulations for the pair correlation function. However, with a slightly modified critical free volume, the results can be made quite acceptable.

Journal Article↗
PubMed2006

Modified lithium borohydrides for reversible hydrogen storage.

In an attempt to develop lithium borohydrides as reversible hydrogen storage materials with high hydrogen storage capacities, the feasibility of reducing the dehydrogenation temperature of the lithium borohydride and moderating rehydrogenation conditions was explored. The lithium borohydride was modified by ball milling with metal oxides and metal chlorides as additives. The modified lithium borohydrides released 9 wt % hydrogen starting from 473 K. The dehydrided modified lithium borohydrides absorbed 7-9 wt % hydrogen at 873 K and 7 MPa. The modification with additives reduced the dehydriding starting temperature from 673 to 473 K and moderated the rehydrogenation conditions from 923 K/15 MPa to 873 K/7 MPa. XRD and SEM analysis revealed the formation of an intermediate compound that might play a key role in changing the reaction path, resulting in the lower dehydriding temperature and reversibility. The reversible hydrogen storage capacity of the oxide-modified lithium borohydrides decreased gradually during hydriding/dehydriding cycling. One of the possible reasons for this effect might be the loss of boron during dehydrogenation, but this can be prevented by changing the dehydriding path using appropriate additives. The additives reduced the dehydriding temperature and improved the reversibility, but they also reduced the hydrogen storage capacity. The best compromise can be reached by selecting appropriate additives, optimizing the additive loading, and using new synthesis processes other than ball milling.

Journal Article↗
PubMed2005

Underpotential deposition of hydrogen on benzene-modified Pt(111) in aqueous H2SO4.

The Pt(111) electrode is modified by an overlayer of C6H6 (ads) upon its cycling in the 0.05-0.80 V range in aq H2SO4 + 1 mM C6H6. The C6H6 (ads) overlayer significantly changes the underpotential-deposited H (H(UPD)) and anion adsorption, and cyclic-voltammetry (CV) profiles show a sharp cathodic peak and an asymmetric anodic one in the 0.05-0.80 V potential range. The C6H6 (ads) layer blocks the (bi)sulfate adsorption but facilitates the adsorption of one monolayer of H(UPD). Cycling of the benzene-modified Pt(111) in benzene-free aq 0.05 H2SO4 from 0.05 to 0.80 V results in a partial desorption of C6H6 (ads) and in a partial recovery of the CV profile characteristic of an unmodified Pt(111). The peak potential of the cathodic and anodic feature is independent of the scan rate, s (10 < or = s < or = 100 mV s(-1)), and the peak current density increases linearly with an increase of the scan rate. Temperature variation modifies the peak potential and current density but does not affect the charge density of the cathodic or anodic feature. Temperature-dependent studies allow us to determine the thermodynamic state function for the H(UPD) adsorption and desorption. Delta G degrees(ads)(H(UPD))assumes values from -4 to -12 kJ mol(-1), while has values from 9 to 14 kJ mol(-1). The values of delta Delta G degrees (delta Delta G degrees = delat Delta G degrees(ads) + delta Delta D degrees(des)) decrease almost linearly from 6 kJ mol(-1) at theta(H(UPD) --> 0 to 0 kJ mol(-1) at theta(H(UPD) --> 1. The nonzero values of delta Delta G degrees testify that the adsorbing and desorbing H(UPD) adatoms interact with an energetically different substrate. The lateral interactions changed from repulsive (omega = 29 kJ mol(-1) at theta(H(UPD) --> 0) to attractive (omega = -28 kJ mol(-1) at theta(H(UPD) --> 1) as the H(UPD) coverage increases. The values of delta S degrees(ads)(H(UPD)) increase from 19 to 56 J K(-1) mol(-1), while those of delta S degrees(des)(H(UPD)) decrease from 45 to -30 J K(-1) mol(-1) with an increase of H(UPD) coverage. The values of delta H degrees(des)(H(UPD)) and delta H degrees(des)(H(UPD)) vary from 0 to 27 kJ mol(-1). The Pt(111)-H(UPD) surface bond energy at the benzene-modified Pt(111) electrode falls in the 191-218 kJ mol(-1) range and is weaker than in the case of the unmodified Pt(111) electrode in the same electrolyte.

Journal Article↗
PubMed2006

Micropatterning of copper on a poly(ethylene terephthalate) substrate modified with a self-assembled monolayer.

We have developed a technique for the site-selective electroless deposition of Cu on poly(ethylene terephthalate) (PET) substrate modified with an organic self-assembled monolayer (SAM). The PET substrate was first modified with a silica-like layer by being dip-coated in an acetone solution of 3-aminopropyltrimethoxysilane and treated with UV light. The PET substrate was further modified with thiol groups using a 3-mercaptopropyltrimethoxysilane-SAM and then irradiated by UV light through a photomask to prepare thiol-group regions and OH-group regions. Cu was then deposited on only the thiol-group regions of the substrate by electroless deposition in a neutral solution with no catalysts by using dimethylamineborane as a reducing reagent. This site-selective deposition process can control the deposition conditions by an organic thin film fabricated on a surface-modified PET substrate, and thus can be applied to other low heat-resistant substrates.

Journal Article↗
PubMed2006

Polyoxometalate-modified carbon nanotubes: new catalyst support for methanol electro-oxidation.

A new catalyst support, polyoxometalate-modified carbon nanotubes, is presented in this paper through the chemisorption between polyoxometalate and carbon. Pt and Pt-Ru nanoparticles were electrochemically deposited on polyoxometalate-modified carbon nanotubes electrodes, and their electrocatalytic properties for methanol electro-oxidation are investigated in detail. Due to the unique electrical properties of carbon nanotubes and the excellent redox properties and the high protonic conductivity of polyoxometalate, for the similar deposition charge of Pt and Pt-Ru catalysts, 1.4 times larger exchange current density, 1.5 times higher specific activity, and better cycle stabilities can be obtained at polyoxometalate-modified carbon nanotube electrodes as compared to the electrodes without polyoxometalate modification. These results show that polyoxometalate-modified carbon nanotubes as a new catalyst support have good potential application in direct methanol fuel cells.

Journal Article↗
PubMed2006

Structural and mechanistic investigation of a phosphate-modified HZSM-5 catalyst for methanol conversion.

Phosphorus modification of a HZSM-5 (MFI) zeolite by wet impregnation has long been known to decrease aromatic formation in methanol conversion chemistry. We prepared and studied a catalyst modified by introducing trimethylphosphine under reaction conditions followed by oxidation. Magic-angle spinning (MAS) NMR shows that extensive dealumination occurs, resulting in a catalyst with a much higher framework SiO2/Al2O3 ratio, as well as extraframework aluminum and approximately 1.4 equiv of entrained phosphoric acid (under working conditions) per aluminum. Upon dehydration or regeneration, the phosphoric acid is converted, reversibly, to entrained P4O10. The aromatic selectivity of the modified catalyst is significantly lower than that of an unmodified zeolite with a similar, increased framework SiO2/Al2O3 ratio. By comparing the rates of H/D exchange in propene under conditions similar to those in methanol conversion chemistry, we determined that the acid site strength is indistinguishable on modified and unmodified zeolites, and this is consistent with theoretical modeling. On the phosphorus-modified zeolite, the rate of propene oligomerization is greatly suppressed, suggesting that entrained phosphate is an impediment to sterically demanding reactions.

Journal Article↗
PubMed2000

A novel approach for analyzing the structure of DNA modified by Benzo[a]pyrene diol epoxide at single-molecule resolution.

Benzo[a]pyrene diol epoxide (BPDE) has been shown to bind specifically to the exocyclic amino group of deoxyguanosine in duplex DNA. Interestingly, this metabolite exhibits stereoselectivity in its tumorigenic and mutagenic effects. It is thought that local DNA conformation is altered at the site of the adduct, resulting in aberrant biological processes, and that in certain sequence contexts BPDE-DNA adducts induce bends in the DNA. In the work presented here, we compared DNA structural alterations of BPDE-modified DNA and unmodified DNA via tapping mode atomic force microscopy (AFM). DNA fragments 366 base pairs (bp) in length were generated by PCR from the duplicated multiple-cloning site of pBEND2 inserted into pGEM-3Zf(-), and either mock-modified or treated with BPDE to give modification levels between 1 and 5% of the nucleotides. Control or BPDE-modified DNA was adsorbed to mica and visualized in air by AFM. The contour lengths and end-to-end lengths of individual molecules were measured. The ratio of end-to-end distance to contour length was significantly smaller for modified DNA molecules than for the unmodified DNA preparation, although the frequency distributions of the contour lengths were similar for the two preparations. This suggests BPDE-DNA adducts cause significant bending of DNA molecules, confirming previous conclusions based on more indirect measurements. The average induced bend angle for BPDE-DNA adducts is estimated to be at least 30 degrees.

Benzopyrenes↗
PubMed1998

The modified Steiner stain: a new use for an old stain? Staining cytomegalovirus-infected cells in gastrointestinal biopsies.

The modified Steiner stain is a non-specific silver stain for identifying bacteria in formalin-fixed, paraffin-embedded tissues. The principle behind its use is that bacteria are first sensitized using uranyl nitrate solution, making them able to precipitate silver from a silver nitrate solution. It is used routinely for staining gastric biopsies to identify Helicobacter pylori. Upon staining a gastric biopsy from a patient with acquired immunodeficiency syndrome (AIDS) and cytomegalovirus gastritis, we recognized that this technique also stains the viral inclusions of cytomegalovirus-infected cells. We then proceeded to stain 43 consecutive cytomegalovirus-positive gastrointestinal biopsies from 33 immunocompromised patients based on positive cytomegalovirus immunohistochemistry (DAKO-cytomegalovirus monoclonal antibody, clones DDG9 and CCH2). We also stained eight cytomegalovirus-infected, non-gastrointestinal tissues, including lung, adrenal gland, ovary, skin and neural tissue, to ensure that the stain was staining the cytomegalovirus-infected cells and not argyrophilic or argentaffin neuroendocrine cells of the gastrointestinal tract. In 40 of the 43 cytomegalovirus-infected gastrointestinal biopsies, we saw positive staining with the modified Steiner stain (93% sensitivity). The cytomegalovirus-infected, non-gastrointestinal tissues all stained positively with the modified Steiner stain. Because the modified Steiner stain is frequently used to identify Helicobacter pylori in gastric biopsies, we propose that it be studied further for possible use either as a screen or as a confirmatory tool, or both, for cytomegalovirus inclusions in gastrointestinal biopsies.

Cell Nucleus↗
PubMed1997

Lysine-rich modified gamma-zeins accumulate in protein bodies of transiently transformed maize endosperms.

During maize seed development, endosperm cells synthesize large amounts of storage proteins, alpha-, beta-, and gamma-zeins, which accumulate within endoplasmic reticulum (ER)-derived protein bodies. The absence of lysine in all zein polypeptides results in an imbalance in the amino acid composition of maize seeds. We modified the maize gamma-zein gene through the introduction of lysine-rich (Pro-Lys)n coding sequences at different sites of the gamma-zein coding sequence. Maize endosperms were transiently transformed by biolistic bombardment with Lys-rich gamma-zein constructs under the control of the 1.7 kb gamma-zein seed-specific promoter and the cauliflower mosaic virus (CaMV) 35S promoter. When (Pro-Lys)n sequences were inserted contiguous to or in substitution of the Pro-Xaa region of the gamma-zein, high levels of protein were observed. In contrast, when (Pro-Lys)n sequences were inserted five residues from the C-terminal, the transcript was present but modified protein was not detected. These results suggest that only an appropriate positioning of Lys-rich inserts leads to the modified molecule displaying correct folding and stability. Subcellular localization analyses and immunoelectron microscopy studies on isolated protein bodies demonstrated that modified gamma-zeins accumulate within these organelles and co-localized with endogenous alpha- and gamma-zeins. The studies reported here show the feasibility of manipulating the gamma-zein gene in order to obtain stable and correctly targeted Lys-rich zeins in maize seeds.

Cloning, Molecular↗
PubMed2000

The validity of the modified patient generated index--a quantitative and qualitative approach.

The purpose of this study was to determine the validity of the recently modified patient generated index (PGI) when used as a self-completed postal questionnaire by older people with arthritis. Two postal surveys were used, followed by interviews with a theoretically chosen sub-sample of respondents to both. Data from the self-completed modified PGI and the arthritis impact measurement scales (AIMS) and the interviews were assessed against 10 pre-defined validity criteria. A total number of 1027 people over 65 years old and with arthritis were surveyed and 53 were selected for interview. The response rates to the two-part survey were 78 and 83%. Complete data for the validity analysis were available from 47% of the respondents. The modified PGI met four and failed to meet six validity criteria. Pre-defined correlations were found with the AIMS and differentiation was possible between respondents with mild, moderate and severe arthritis and between those who had recently sought medical attention and those who had not. The areas that had been chosen for inclusion in the modified PGI were affected by arthritis but may not have been the 'most important' areas. The measurement method could not detect changes in health nor differentiate between respondents taking and not taking analgesics. There were several problems in the respondents' interpretation of the instructions, which were only revealed during the interviews. These data should help inform further modification of the PGI.

Aged↗
PubMed2001

Enzymes of a new modified ortho-pathway utilizing 2-chlorophenol in Rhodococcus opacus 1CP.

Chlorocatechol 1,2-dioxygenase (CC 1,2-DO), chloromuconate cycloisomerase (CMCI), chloromuconolactone isomerase (CMLI), and dienolactone hydrolase (DELH), the key enzymes of a new modified ortho-pathway in Rhodococcus opacus 1CP cells utilizing 2-chlorophenol via a 3-chlorocatechol branch of a modified ortho-pathway, were isolated and characterized. CC 1,2-DO showed the maximum activity with 3-chlorocatechol; its activity with catechol and 4-chlorocatechol was 93 and 50%, respectively. The enzyme of the studied pathway had physicochemical properties intermediate between the pyrocatechase of ordinary and chlorocatechase of modified pathways described earlier for this strain. In contrast to the enzymes investigated earlier, CMCI of the new pathway exhibited high substrate specificity. The enzyme had Km for 2-chloromuconate of 142.86 microM, Vmax = 71.43 U/mg, pH optimum around 6.0, and temperature optimum at 65 degrees C. CMCI converted 2-chloromuconate into 5-chloromuconolactone. CMLI converted 5-chloromuconolactone into cis-dienolactone used as a substrate by DELH; this enzyme did not convert trans-dienolactone. DELH had Km for cis-dienolactone of 200 microM, Vmax = 167 U/mg, pH optimum of 8.6, and temperature optimum of 40 degrees C. These results confirm the existence of a new modified ortho-pathway for utilization of 2-chlorophenol by R. opacus 1CP.

Bacterial Proteins↗
PubMed1998

Screening for PTSD in a substance abuse sample: psychometric properties of a modified version of the PTSD Symptom Scale Self-Report. Posttraumatic stress disorder.

The high rate of posttraumatic stress disorder (PTSD) among substance use disorder (SUD) patients has been documented in research protocols, but there is evidence that it is markedly under-diagnosed in clinical settings. To address the need for a brief self-report measure to identify SUD patients who may benefit from further assessment and/or treatment for PTSD, the psychometric properties of a modified version of the PTSD Symptom Scale Self-Report (PSS-SR) were examined in a treatment-seeking SUD sample (N = 118). The modified version of the PSS-SR, which measures both frequency and severity of PTSD symptoms, demonstrated good internal consistency reliability and was correlated with other self-report measures of trauma-related symptomatology. Comparisons between a structured PTSD diagnostic interview and the modified PSS-SR indicated that 89% of the PTSD positive patients were correctly classified by the modified PSS-SR. The clinical relevance of these findings was discussed.

Adolescent↗
PubMed2003

Comparison of standard and modified SPT method.

BACKGROUND: The aim of our study was to compare clinical significance and economical factors of commonly used standard skin prick tests (SPT) method with new, modified and more handy way of performing SPT. METHODS: Twenty-one subjects [with an average age of 23 years (SD +/- 2.72)] with known sensitivity to examined allergen extracts were tested with histamine, negative control solution and standard allergen extracts (Allergopharma, Reinbeck, Germany). SPT were applied to the volar surface of randomly assigned forearm with two methods: standard technique using lancet needle to prick the epidermis under small drop of extract and tested method using lancet needle which was dipped in extract before prick. In this method all extracts were placed in marked, small, plastic chambers. RESULTS: Mean wheal to histamine was 5.49 (standard method) and 5.01 (modified method). There was no statistical difference between the standard and modified method for size of wheal to histamine (P = 0.654) and to allergen extracts (n = 36, P = 0.824, Wilcoxon test). Economical analysis revealed that examined SPT technique is cheaper than standard method. CONCLUSION: Examined method may be considered to be an alternative for performing SPT as it is safe, cheaper and more convenient than standard technique. SUMMARY STATEMENT: Comparison of standard and modified SPT method revealed the new method to be more economical.

Adult↗