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1.
2.
The generation of dendrimers based on poly(propylene imine) with CN end groups [DAB–dend–(CN)
x
] and with palmitoyl end groups [DAB–dend–(C15)
x
] was studied by methods of translational diffusion and viscometry. The volumes of the DAB–dend–(CN)
x
and DAB–dend–(C15)
x
dendrimers and the previously studied DAB–dend–(lacto)
x
dendrimer were compared to evaluate the volumes of the end groups in hybrid dendrimers. The volume of the hybrid dendrimers
compared to that of the initial dendrimers increases proportionally to the number of end groups: this means that the end groups
are predominantly located on the periphery of each molecule, thus ensuring this volume will increase. It is shown that the
volume of the end groups for DAB–dend–(C15)
x
is 3.5 times greater, and for DAB–dend–(lacto)
x
it is 5.0 times greater than that occupied by free mole- cules corresponding to the end groups. The values of the intrinsic
viscosity were compared with the values of the diffusion coefficient and the chemical formula molecular weight.
Received: 7 August 2001 Accepted: 2 November 2001 相似文献
3.
Elodie Boisselier Dr. Liyuan Liang Maria Dalko‐Csiba Dr. Jaime Ruiz Dr. Didier Astruc Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(20):6056-6068
Titrations of commercial diaminobutane (DAB) and polyamidoamine (PAMAM) dendrimers by vitamins C (ascorbic acid, AA), B3 (nicotinic acid), and B6 (pyridoxine) were monitored by 1H NMR spectroscopy using the chemical shifts of both dendrimer and vitamin protons and analyzed by comparison with the titration of propylamine. Quaternarizations of the terminal primary amino groups and intradendritic tertiary amino groups, which are nearly quantitative with vitamin C, were characterized by more or less sharp variations (Δδ) of the 1H chemical shift (δ) at the equivalence points. The peripheral primary amino groups of the DAB dendrimers were quaternarized first, but not selectively, whereas a sharp chemical‐shift variation was recorded for the inner methylene protons near the tertiary amines, thereby indicating encapsulation, when all the dendritic amines were quaternarized. With DAB‐G5‐64‐NH2, some excess acid is required to protonate the inner amino groups, presumably because of basicity decrease due to excess charge repulsion. On the other hand, this selectivity was not observed with PAMAM dendrimers. The special case of the titration of the dendrimers by vitamin B6 indicates only dominant supramolecular hydrogen‐bonding interactions and no quaternarization, with core amino groups being privileged, which indicates the strong tendency to encapsulate vitamins. With vitamin B3, a carboxylic acid, titration of DAB‐G3‐16‐NH2 shows that only six peripheral amino groups are protonated on average, even with excess vitamin B3, because protonation is all the more difficult due to increased charge repulsion, as positive charges accumulate around the dendrimer. Inner amino groups interact with this vitamin, however, thus indicating encapsulation presumably with supramolecular hydrogen bonding without much charge transfer. 相似文献
4.
Aqueous solution diffusion coefficients for G0–G3 PAMAM dendrimers were determined from DOSY-NMR spectroscopy at high and
neutral pH. The study was performed in a dilute regime and diffusion coefficients at infinite dilution (D
0) were estimated from the variation of diffusion coefficients with dendrimer concentration. Hydrodynamic radii (R
h) for each dendrimer were estimated from D
0 using the Stoke–Einstein relationship at both pH. According to D
0 and R
h values, the structure of G0–G1 PAMAM dendrimers is almost insensitive to pH variations, whereas G2–G3 PAMAM dendrimers undergo
swelling at neutral pH, due to surface amino groups protonation. Experimental diffusion coefficients show a scaling trend
with the number of dendrimer atoms (N), with scaling laws of the type D0 μ Na D_{0} \propto N^{\alpha } , where α takes values of −0.39 and −0.50 at pH 12 and 7, respectively. For the first time, experimental data accounts for the scaling
behavior of aqueous diffusion coefficients for low generation PAMAM dendrimers, as previously reported from molecular dynamics
simulations. 相似文献
5.
B. Miksa S. Slomkowski M. M. Chehimi M. Delamar J.-P. Majoral A.-M. Caminade 《Colloid and polymer science》1999,277(1):58-65
Quartz plates were modified by consecutive immobilization of γ-aminopropyltriethoxysilane (APTS), phosphorus containing dendrimers
with aldehyde groups (generation 5 – G5), Starburst PAMAM dendrimers generation 4 (G4-PAMAM), and poly(styrene/acrolein/divinylbenzene)
microspheres [P(SAD)]. In this way surfaces with heterogeneity on molecular, macromolecular, and microscopic levels, and which
were equipped with functional amino or aldehyde groups were obtained. Surface layers were characterized by X-ray photoelectron
spectroscopy (XPS) and by contact-angle measurements. Analysis of XPS spectra revealed that the thickness of the layer of
G5 on the SiO2-APTS substrate was 3.7 nm, i.e., the thickness was typical for macromolecular dimensions. The average thickness of the layer
of PAMAM dendrimers on SiO2-APTS-G5 was found to be 0.35 and 0.29 nm, depending on whether calculations were based on attenuation of the intensity of
the Si2p or the P2p signal respectively. This thickness was unreasonably low for a monolayer of PAMAM dendrimers and indicated that the surface
of the SiO2-APTS-G5 substrate was incompletely covered with these macromolecules. The XPS method was also used for the determination
of the degree of coverage of the surface of a SiO2-APTS-G5-PAMAM plate with P(SAD) microspheres. The degree of coverage was found to be 0.60 and approaches the maximum theoretically
possible value (0.62) for microspheres attached chaotically and irreversibly to the surface in an arrangement one microsphere
thick. Subsequent coverage of the SiO2-APTS-G5-PAMAM-P(SAD) substrate with PAMAM dendrimers resulted in the formation of a PAMAM adlayer 3.2 nm thick, close to
the molecular dimensions of these dendrimers. Contact-angle measurements revealed considerable differences in the hydrophobicity
of the surfaces of the quartz plates, depending on their modification. Hydrophobicity increased in the order SiO2 < SiO2-APTS-G5-PAMAM < SiO2-APTS ≤ SiO2-APTS-G5 < SiO2-APTS-G5-PAMAM-P(SAD).
Received: 17 March 1998 Accepted: 14 September 1998 相似文献
6.
Prof. Dr. Long‐Li Lai Sheng‐Wei Wang Dr. Kung‐Lung Cheng Dr. Jey‐Jau Lee Tsai‐Hui Wang Prof. Dr. Hsiu‐Fu Hsu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(48):15361-15367
Two triazine‐based unconventional dendrimers were prepared and characterized by 1H and 13C NMR spectroscopy, mass spectrometry, and elemental analysis. Differential scanning calorimetry, polarizing microscopy, and powder XRD studies showed that these dendrimers display columnar liquid‐crystalline phases during thermal treatment. This is ascribable to breaking of their C2 symmetry. The molecular conformations of prepared dendrimers were obtained by computer simulation with the MM3 model of the CaChe program in the gas phase. The simulation showed that the conformations of the prepared dendrimers are rather flat and disfavor formation of the LC phase. However, due to C2‐symmetry breaking, the prepared dendrimers have structural isomers in the solid state and thus show the desired columnar phases. This new strategy should be applicable to other types of unconventional dendrimers with rigid frameworks. 相似文献
7.
Huricha Baigude Kaname Katsuraya Kousaku Okuyama Yoshihide Yachi Shoma Sato Toshiyuki Uryu 《Journal of polymer science. Part A, Polymer chemistry》2002,40(21):3622-3633
A reactive three‐layered dendrimer containing carboxyl groups was synthesized by the coupling of dicarboxylic acid and a highly reactive, two‐layered glycopeptide dendrimer. Lactose, maltose, or maltotriose was reacted with the poly(lysine) dendrimer in its third and fourth generations by reductive amination and afforded two‐layered glycolysine dendrimers. The reaction was conducted in a borate buffer (pH 9.0). 1H NMR, 13C NMR, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analyses were applied for the determination of the structures of the products. When an excess amount of the oligosaccharide and a long reaction time were used, the degree of substitution increased to 1.5–2.0 against an amino group. For the preparation of highly reactive, multilayered dendrimers for an antigen carrier, C6 hydroxy groups of the oligosaccharides were selectively esterified by adipic acid and suberic acid to give 6‐O‐adipoyl oligosaccharide–poly(lysine) dendrimers and 6‐O‐suberoyl oligosaccharide–poly(lysine) dendrimers. The reactivity of these multilayered dendrimers was examined by a model reaction with phenylalanine ethyl ester. The dendrimer showed high reactivity, providing phenylalanine ethyl ester–dicarboxylate oligosaccharide–poly(lysine) dendrimers with a considerably high proportion of phenylalanine residues. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3622–3633, 2002 相似文献
8.
S. K. Ignatov A. A. Bagatur'yants A. G. Razuvaev M. V. Alfimov M. B. Molotovshckikova V. A. Dodonov 《Russian Chemical Bulletin》1998,47(7):1257-1265
The structural, electronic, and energy parameters of the metal-containing clusters (H3SiO)3Si−O−XMe
n
(X=H, B, Al, or Zn;n=0, 1, or 2), which model organometallic groups on a SiO2 surface modified with B-, Al-, and Zn-containing alkyls, have been studied by quantum-chemical methods. Full geometry optimization
for these clusters was carried out by the SCF MO LCAO method taking into account the electron correlation within the frameworks
of the MP2 and B3LYP schemes using the 6-31G(d) (6-311G(d) for Zn) basis set. The effect of the crystal environment was taken
into account in calculations of siliconoxygen clusters containing 10 and 30 silicon atoms using theab initio SCF/6-31G(d) and semiempirical MNDO-PM3 methods. Various modes of coordination and interactions of organometallic groups
with oxygen atoms of surface groups were studied. For the organoaluminum group on the surface, two stable conformations were
found, namely, the three-coordinate structure with the chain −O−AlMe2 ligand and the four-coordinate (quasicyclic) structure with the Al atom that forms two nonequivalent bonds with the O atoms
at the same Si atom. The four-coordinate structure is energetically more favorable. No stable structures were found for the
organoboron and organozinc fragments.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1296–1303, July, 1998. 相似文献
9.
S. V. Timofeev V. I. Bregadze S. N. Osipov I. D. Titanyuk P. V. Petrovskii Z. A. Starikova I. V. Glukhov I. P. Beletskaya 《Russian Chemical Bulletin》2007,56(4):791-797
New alanine derivatives containing both the carboranyl and trifluoromethyl groups were synthesized by the reaction of organometallic
derivatives of o-carborane with methyl trifluoropyruvate imines. When using the 1R-(−)-menthoxycarbonyl protecting group at the nitrogen atom, one of diastereomers was isolated and characterized. Trifluoromethyl-carboranylalanine
methyl esters containing different protecting groups at the nitrogen atom were studied by X-ray diffraction. Both complete
and partial deprotection of the amino and carboxy groups was performed.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 761–767, April, 2007. 相似文献
10.
Theoretical and experimental characterization of amino‐PEG‐phosphonate‐terminated Polyphosphorhydrazone dendrimers: Influence of size and PEG capping on cytotoxicity profiles
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Aurélien Hameau Séverine Fruchon Christian Bijani Alessandro Barducci Muriel Blanzat Rémy Poupot Giovanni M. Pavan Anne‐Marie Caminade Cédric‐Olivier Turrin 《Journal of polymer science. Part A, Polymer chemistry》2015,53(6):761-774
The synthesis of new series of PPH (poly(phosphorhydrazone)) dendrimers with amino‐PEG phosphonates or the corresponding amino‐PEG phosphonic acids as terminal groups is presented, from generations 1–3. The size of PEG‐terminated dendrimers is experimentally measured by diffusional NMR, and by means of dynamic light scattering. Classical molecular dynamics and well‐tempered metadynamics simulations are used to assess or confirm the formation of aggregates in some cases. The influence of PEG capping on the cytotoxicity profiles of the dendrimers is evaluated on human peripheral blood mononuclear cells by means of LIVE/DEAD assays, and confirms the importance of PEG capping to ensure low cytotoxicity. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 761–774 相似文献
11.
V.L. Furer A.E. Vandyukov I.I. Vandyukova J.P. Majoral A.M. Caminade V.I. Kovalenko 《Vibrational Spectroscopy》2009,51(2):326-332
The FTIR spectra of four generations of phosphorus-containing dendrimers built of thiophosphoryl, cyclophosphazene and phthalocyanine cores with terminal benzaldehyde and P–Cl groups have been recorded and analyzed. FT-Raman spectra of four generations of phosphorus dendrimers built of cyclotriphosphazene core with terminal benzaldehyde groups have been detected. Their spectral pattern is determined by the ratio Tn/Rn (Tn—number of terminal groups, Rn—number of repeating units). This ratio trends to r − 1 (r—branching functionality of repeating unit), and becomes constant, when the generation number is higher than 3. Experimental IR spectra of dendrimers built of thiophosphoryl, cyclophosphazene and phthalocyanine cores are very closely similar. The dependence of band full width at half height in IR spectra on the number of dendrons is established. The possibility appears to separate the bands assigned to the core, repeating units and terminal groups of dendrimers by difference spectroscopy method. 相似文献
12.
A. I. Lysachkov N. I. Boiko E. A. Rebrov A. M. Muzafarov V. P. Shibaev 《Russian Chemical Bulletin》2007,56(12):2407-2413
Second-generation (G-2) liquid-crystalline carbosilane block and statistical dendrimers with aliphatic (decyl) and photochromic
(azobenzene-containing) mesogenic terminal groups and a G-2 homo-dendrimer containing the same mesogenic terminal groups were
synthesized for the first time. The influence of dendritic architecture on the phase behavior of the dendrimers and on photoinduced
Z-E-isomerization of the azobenzene fragments in mesogenic terminal groups in dendrimer solutions are discussed.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2325–2331, December, 2007. 相似文献
13.
Lebedev B. V. Ryabkov M. V. Tatarinova E. A. Rebrov E. A. Muzafarov A. M. 《Russian Chemical Bulletin》2003,52(3):545-551
Temperature dependences of the specific heats, characteristic temperatures, and enthalpies of physical transformations of the first to fifth generations of carbosilane dendrimers with allyl terminal groups were studied using an adiabatic vacuum calorimeter in the temperature range 6—340 K. The error of measurements was, as a rule, about 0.2%. Thermodynamic characteristics of physical transformations of the dendrimers were determined and their thermodynamic functions C
p°(T), H°(T)—H°(0), S°(T)—S°(0), and G°(T)—H°(0) were calculated for the temperature range 0—340 K. The thermodynamic functions of the dendrimers are linearly related to their molecular weights, the number of allyl groups on their outer spheres, and the number of moles of diallylmethylsilane per mole of the dendrimers formed. Additive dependence of the properties of the dendrimers on their chemical composition and structure indicates that the energy of interaction between structural fragments of the dendrimers is independent of the dendrimer generation number. The fractal dimensions, D, of all dendrimers studied in this work are 1.2—1.3 in the temperature range 30—50 K, thus indicating a chain-layered structure of the dendrimer glasses. 相似文献
14.
N. N. Smirnova O. V. Stepanova T. A. Bykova A. V. Markin E. A. Tatarinova A. M. Muzafarov 《Russian Chemical Bulletin》2007,56(10):1991-1995
Temperature dependences of the heat capacity of carbosilane dendrimers with butyl terminal groups of the seventh and ninth
generations were determined in the temperature range from 6 to 600 K by precision adiabatic vacuum calorimetry and differential
scanning (dynamic) calorimetry. The physical transitions were revealed and their thermodynamic characteristics were analyzed.
The experimental data obtained were used to calculate the standard thermodynamic functions C
p
(T), H°(T) − H°(0), S°(T), and G°(T) − H°(0) for the temperature range from T → 0 to 600 K. The thermodynamic function-molar weight isotherms for the dendrimers of the third–ninth generations with terminal
butyl groups in the glassy and highly elastic state are linear.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1924–1928, October, 2007. 相似文献
15.
Li Z Valentine SJ Clemmer DE 《Journal of the American Society for Mass Spectrometry》2011,22(5):817-827
Complexation of a series of related amino compounds by 18-crown-6 ether (18C6) is studied as a means of improving the resolution
of mixtures by combinations of ion mobility spectrometry (IMS) and mass spectrometry (MS) techniques. Mixtures of the isomeric
amines n-octylamine (NOA), dibutylamine (DBA), and diisopropylethylamine (DIPEA) were electrosprayed to produce gaseous [M
+ H]+ ions. These species have overlapping mobilities and are not resolved by IMS. Addition of 18C6 yields [M + 18C6 + H]+ ion complexes that are resolved by IMS. In subsequent experiments, [M + 18C6 + H]+ ion complexes are separated according to their mobilities and specific species are selected and exposed to collisional activation.
This analysis yields dissociation voltages that are inversely correlated with the number of separate substitutions on the
nitrogen atom of the amino compounds; dissociation voltages of ~40, ~90, and ~150 V are obtained for the tri-, di-, and mono-substituted
amino compounds DIPEA, DBA, and NOA, respectively. For these complexes, an inverse correlation is also observed with respect
to the gas-phase basicities (GB) of the amino compounds (964, 935, and 895 kJ mol−1, respectively). Studies of 18C6 complexes with a series of n-alkylamines (C
n
H2n+3N where n = 3 to 18, respectively) show that dissociation voltages increase systematically (from ~140 to ~190 V) under the conditions
employed. The sensitivity to collision energy provides an additional means of distinguishing between classes of compounds.
The approach is extended as a means of separating nitrogen-containing compounds from petroleum. 相似文献
16.
V. Yu. Korotaev Yu. A. Skorik A. Yu. Barkov M. I. Kodess A. Ya. Zapevalov 《Russian Chemical Bulletin》2005,54(11):2545-2549
3,3,3-Trifluoro-N′-(3-trifluoromethylphenyl)-1,2-propanediamine (5) was synthesized by the reaction of 2-diazo-1,1,1-trifluoro-3-nitropropane or 3,3,3-trifluoro-1-nitropropene with 3-aminobenzotrifluoride
followed by the reduction of the nitro group. The Michael 1,4-addition of diamine 5 to acrylic acid occurs only at the N(1) atom and affords N-mono-or N,N-dicarboxyethyl derivatives 6 and 7, depending on the reactant ratio. Protolytic equilibria 5–7 in aqueous solutions were studied by pH-potentiometry and UV spectroscopy. Only the aliphatic amino group can be protonated
in an aqueous solution, while the aromatic amino group remains unprotonated even in 12 M HCl. The stability constants of transition metal (Cu2+, Ni2+, Zn2+) complexes with ligands 5–7 were determined by pH-potentiometric titration. The stability of the complexes and selectivity of the ligands toward Cu2+ ions increase with an increase in the number of N-carboxyethyl groups.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2465–2469, November, 2005. 相似文献
17.
In this paper, we synthesized a range of amphiphilic Janus dendrimers, which consisted of acidic amino acid and naproxen molecules as the peripheral groups, as novel potential bone-targeting dendritic drug delivery. These dendrimers take advantage of a dendritic display to carry multiple drug molecules and targeting moieties simultaneously. All of the dendrimers exhibited more than 80% binding rates to hydroxyapatite (HAP), especially the [G2]-dendrimers (2a and 2b) showed dramatic binding rates (>95%). Moreover, the solubility of naproxen was remarkably enhanced by the dendritic drug delivery system, especially the naproxen concentration of 2b achieved 5.37 mg/ml, which is more than 28-fold over that of native drug. Furthermore, cell viability studies showed that all the dendrimers exhibited no significant cytotoxicity against HEK293 cells. These results provided an effective entry to the development of new bone-targeting drugs. 相似文献
18.
Folding dynamics and energy landscape picture of protein conformations of HP-36 andβ-amyloid (Aβ) are investigated by extensive Brownian dynamics simulations, where the inter amino acid interactions are given by a minimalistic
model (MM) we recently introduced [J. Chem. Phys.
118 4733 (2003)]. In this model, a protein is constructed by taking two atoms for each amino acid. One atom represents the backbone
Cαs atom, while the other mimics the whole side chain residue. Sizes and interactions of the side residues are all different
and specific to a particular amino acid. The effect of water-mediated folding is mapped into the MM by suitable choice of
interaction parameters of the side residues obtained from the amino acid hydropathy scale. A new non-local helix potential
is incorporated to generate helices at the appropriate positions in a protein. Simulations have been done by equilibrating
the protein at high temperature followed by a sudden quench. The subsequent folding is monitored to observe the dynamics of
topological contacts (N
topo
), relative contact order parameter (RCO), and the root mean square deviation (RMSD) from the real-protein native structure.
The folded structures of different model proteins (HP-36 and Aβ) resemble their respective real native state rather well. The dynamics of folding showsmultistage decay, with an initial hydrophobic collapse followed by a long plateau. Analysis ofN
topo
and RCO correlates the late stage folding with rearrangement of the side chain residues, particularly those far apart in
the sequence. The long plateau also signifies large entropic free energy barrier near the native state, as predicted from
theories of protein folding.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献
19.
Yu. A. Borisov Yu. A. Zolotarev E. V. Laskatelev N. F. Myasoedov 《Russian Chemical Bulletin》1998,47(8):1442-1445
Ab initio calculations of molecular and electronic structures of neutral molecules and protonated forms of methionine and its derivatives
in the gaseous phase were carried out by the Hartree-Fock method using the 6–31G* basis set with full geometry optimization. Proton affinities of methionine (1), methionine sulfoxide (2), and methionine
sulfone (3) were calculated for different modes of coordination of the proton. The results of calculations demonstrated that
in protonated forms of 1 and 3, bonding between the proton and the N atom is most favorable, while in protonated form of 2,
bonding between the proton and the O atom of the SO group is most favorable. The proton affinities of the amino acids are
as follows: 223.2 (1), 241.2 (2), and 221.5 (3) kcal mol−1,i.e., methionine sulfoxide 2 exhibits the highest proton affinity in the series of the amino acids under consideration.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1487–1490, August, 1998. 相似文献
20.
Prof. Dr. Long‐Li Lai Shun‐Ju Hsu Hui‐Chu Hsu Sheng‐Wei Wang Dr. Kung‐Lung Cheng Chun‐Jung Chen Tsai‐Hui Wang Prof. Dr. Hsiu‐Fu Hsu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(21):6542-6547
Two series of unconventional triazine‐based dendrimers with C2 symmetry and C3 symmetry were prepared. The newly prepared C3‐symmetrical dendrimers were characterized by 1H and 13C NMR spectroscopy, mass spectrometry, and elemental analysis. Differential scanning calorimetry, polarizing microscopy, and powder XRD showed that the C3‐symmetrical dendrimers display columnar liquid‐crystalline phases during thermal treatment, but the C2‐symmetrical dendrimers were not observed to behave correspondingly. The molecular conformations of C3‐ and C2‐symmetrical dendrimers were obtained by computer simulation with the MM2 model of the CaChe program in the gas phase. The simulation results reasonably explain the different mesogenicities of C3‐ and C2‐symmetric dendrimers. This new strategy should be applicable to other types of unconventional dendrimers with rigid frameworks for displaying columnar liquid‐crystalline behavior. 相似文献