Investigation of the state and dynamics of water in hydrogels of cellulose ethers by 1H NMR spectroscopy

The aim of this work was to study the effect of the type of substituent of the cellulose ethers and the molecular mass on the state and dynamics of water in the respective hydrogels to specify the quantity of adsorbed water on the polymers or, more explicitly, to calculate the average number of water molecules bound to a polymer repeating unit (PRU).¹H NMR relaxation experiments were performed on equilibrated systems of cellulose ether polymers (HEC, HPC, HPMC K4M, and HPMC K100M) with water. In particular, the water proton spinlattice (T ₁) and spin-spin (T ₂) relaxation times were measured in these systems at room temperature. The observed proton NMRT ₁ andT ₂ of water in hydrogels at different cellulose ether concentrations at room temperature were shown to decrease with increasing polymer concentration. The relaxation rate 1/T ₁ is sensitive to the type of polymer substituent but insensitive to the polymer molecular mass. The rate 1/T ₂ appears much less influenced by the polymer substitution. The procedure developed for calculating the amount of water bound per PRU, based on the analysis of theT ₁ andT ₂ data, shows that this amount is the largest for HPC followed by HEC, HP MC K4M, and HPMC K100M. The results correlate well with the degree of hydrophilic substitution of the polymer chains. This NMR analysis deals with a single molecular layer of adsorbed water for the investigated cellulose ether polymers at all concentrations, while the rest of the water in the hydrogel is bulk-like. Therefore, the mesh size of polymer network in the view of a single molecular layer is not effectively changed.     

The reaction between neutral salts and fibrous proteins. I. The model system sodium poly-L-glutamate-LiBr-H 2 O

The effects of concentrated aqueous solutions of a neutral salt, lithium bromide, on randomly coiled sodium poly-L -glutamate have been followed using high resolution infrared and nuclear magnetic resonance spectroscopy. The results suggest that two processes are taking place. First, at low concentrations 0–4M LiBr, a simple electrolyte effect occurs in which some water is removed from the polymer by an electrostriction effect. Second, a more intense interaction (>4M LiBr), apparently cooperative, occurs in which the competition for the available water in the system forces the electrolyte to form an association with the peptide group either as a fully or partially hydrated species. It is proposed that the anion is associated with the nitrogen atom of the peptide group and the cation is situated within the vicinity of the carbonyl oxygen.     

Calculations on the effect of methylation on the electrostatic stability of the B- and Z-conformers of DNA

The three-dimensional Poisson–Boltzmann equation for the distribution of counterion charge density around double-helical DNA has been solved for solutions of .01M, .10M, and .20M monovalent salt. The polymers, poly[d(CpGp)] and poly[d(m⁵CpGp)], were studied in the B- and the Z-conformations. The effect of methylation on the relative stabilities of these conformers in solutions of different ionic strengths is known to favor the Z-form. Accumulation of charge density around the B- and the Z-conformers is compared in detail. The relative electrostatic stabilities of the B- and Z-conformers in .01M, .10M, and .20M solutions are compared and discussed in terms of the ion–DNA interactions and the self-energy of the structured ionic environment. The ion–DNA interaction energies, termed “phosphate screening,” monotonically decrease with ionic strength and are consistent with a B-to-Z conformation change induced in either polymer by increased electrolyte concentration. However, these calculated energies alone do not account for the fact that the ionic strength at the midpoint of the transition of the methylated polymer is substantially lower than that of its unmethylated analogues. The phosphate screening effect is counterbalanced by changes in the self-energy required for the creation of the structured counterion environment. This self-energy of the electrolyte environment monotonically increases with ionic strength. Methylation-induced shifts in the overall conformational equilibria depend on the relative changes of these competing effects. Increasing salt concentration is calcualted to favor the Z-conformer. The effect of methylation, lowering the ionic strength of the transition midpoint, is proposed to originate in minor structural changes in the Z-form of the polymer, making the groove more accessible to counterions in the G(3′ – 5′)C region. This allows a redistribution of counterion density and a lowering of the self-energy of the ionic environment, conferring added stability to the Z-conformation, as indicated by calculations of relative entropies. The experimentally observed temperature dependence of the B-to-Z transition, however, cannot be explained without assuming the release of bound water. Maps of the calculated three-dimensional structure at the counterion distribution near the surface of these molecules in both the B- and the Z-forms are also presented.     

Miscibility studies of HPMC/PVA blends in water by viscosity, density, refractive index and ultrasonic velocity method

Hydroxy propyl methyl cellulose (HPMC)/polyvinyl alcohol (PVA) blends are edible polymer films used for food packing and directly in foodstuffs. However they are water-soluble in ordinary temperature and have good mechanical properties. The miscibility of HPMC/PVA blend in water was studied by viscosity, ultrasonic velocity, density and refractive index techniques at 30 and 50 °C. Using viscosity data, the interaction parameters μ and α were calculated. These values revealed that HPMC/PVA blend is miscible when the HPMC content is more than 60% in the blend at 30 and 50 °C. And also the result revealed that the change in temperature has no significant effect on the miscibility of HPMC/PVA polymer blend.     

Competition between co-dominant plants of the Serengeti plains depends on competitor identity,water, and urine

Kyllinga nervosa (Steud.) and Sporobolus kentrophyllus (K. Schum.) are co-dominant plants of the Serengeti short-grass plains, Tanzania. The plains are characterized by seasonal and sporadic rainfall and currently support in excess of 1.5 million migratory ungulates. The interactive effect of simulated bovine urine and water availability were tested on the competitive interactions of these species in the laboratory. Sporobolus kentrophyllus was a superior competitor to K. nervosa over the tested treatment levels with respect to growth and reproductive effort. Sporobolus kentrophyllus exhibited rapid growth in response to urine addition, leading to a significant species × urine interaction while reduced growth by K. nervosa in response to low water availability explained the significant species × water interaction and is likely explained by K. nervosa's shallow root system. Kyllinga nervosa, however, appears to be more tolerant of low nitrogen conditions based on its similar growth with and without the urine treatment. The effect of intraspecific competition on total biomass was similar for S. kentrophyllus and K. nervosa. Competition resulted in increased size differences (asymmetry) for K. nervosa and for the interspecific competition treatments compared to the size differences observed for plants grown individually (in absence of competition).Total reproductive biomass was reduced most by competition with S. kentrophyllus, irrespective of target species. The water treatment did not influence reproduction while the urine treatment significantly increased reproductive biomass and interacted with target species, competitor species, and yielded a three-way urine × target × competitor species interaction.Results suggest that codominance of these two species in the Serengeti is regulated by water availability, nitrogen input from grazers, and local neighbor identity.     

Factors influencing stomatal conductance in response to water availability in grapevine: a meta‐analysis

The main factors regulating grapevine response to decreasing water availability were assessed under statistical support using published data related to leaf water relations in an extensive range of scion and rootstock genotypes. Matching leaf water potential (Ψ_leaf) and stomatal conductance (g_s) data were collected from peer‐reviewed literature with associated information. The resulting database contained 718 data points from 26 different Vitis vinifera varieties investigated as scions, 15 non‐V. vinifera rootstock genotypes and 11 own‐rooted V. vinifera varieties. Linearised data were analysed using the univariate general linear model (GLM) with factorial design including biological (scion and rootstock genotypes), methodological and environmental (soil) fixed factors. The first GLM performed on the whole database explained 82.4% of the variability in data distribution having the rootstock genotype the greatest contribution to variability (19.1%) followed by the scion genotype (16.2%). A classification of scions and rootstocks according to their mean predicted g_s in response to moderate water stress was generated. This model also revealed that g_s data obtained using a porometer were in average 2.1 times higher than using an infra‐red gas analyser. The effect of soil water‐holding properties was evaluated in a second analysis on a restricted database and showed a scion‐dependant effect, which was dominant over rootstock effect, in predicting g_s values. Overall the results suggest that a continuum exists in the range of stomatal sensitivities to water stress in V. vinifera, rather than an isohydric–anisohydric dichotomy, that is further enriched by the diversity of scion‐rootstock combinations and their interaction with different soils.     

Induction of a hexagonal phase in phospholipid-surfactant bilayers

The possibility of modifying the curvature of lipid bilayers by mixing them with additives is demonstrated and the evolution of geometrical parameters with composition is discussed. X-ray diffraction patterns of the POPC/C₁₂EO₂/²H₂O system were observed as a function of the relative humidity. The formation of an unexpected hexagonal phase indicates peculiar behaviour in these mixtures. The cylinder radius of this phase is considerably smaller than previously observed in cubic phases. A discussion of the head group interactions is presented. We have also been able to show that the uptake of water by the L _β gel phase is higher as a single phase than in the L _β +H_II two phase region. The water content is important for the stabilization of H_II phase and determination of its characteristic dimensions. However, it is argued that the interaction between the surfactant and the lipid is the key factor for its formation and that the EO₂ head groups displace water from the inner parts of the polar region of the mesogenic units. Received: 22 September 1997 / Revised version: 31 December 1997 / Accepted: 10 February 1998     

Effects of water activity and aqueous solvent ordering on thermal stability of lysozyme, α-chymotrypsinogen A, and alcohol dehydrogenase

Effects of water activity (a_W) and solvent ordering were separately analyzed on the thermal unfolding of lysozyme and α-chymotrypsinogen A, and also on the thermal deactivation of yeast alcohol dehydrogenase (YADH) in aqueous solutions with various additives. With the coexistence of additives, water activity was the determinant of the extent of the change in the thermal stability of proteins while solvent ordering was the determinant of the direction of the change. The parameter α, determined from the activity coefficient of water, representing the deviation of a_W from that of the ideal solution, was useful as a quantitative index of the solvent ordering showing good correlations with the unfolding temperature and enthalpy of lysozyme and α-chymotrypsinogen A and also with the thermal deactivation rate constant of YADH at a constant a_W. Solvent ordering seemed to affect the thermal stability of proteins mainly through its effect on the intramolecular hydrophobic interaction among amino acid residues in a protein molecule but the contribution of the electrostatic interaction including hydrogen bonding through the change in permittivity of solution was also suggested.     

Influence of lipid membrane rigidity on properties of supporting polymer

Temperature-sensitive hydrogel polymers are utilized as responsive layers in various applications. Although the polymer's native characteristics have been studied extensively, details concerning its properties during interaction with biorelated structures are lacking. This work investigates the interaction between a thermoresponsive polymer cushion and different lipid membrane capping layers probed by neutron reflectometry. N-isopropylacrylamide copolymerized with methacroylbenzophenone first supported a lipid bilayer composed of 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) and subsequently 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). The polymer-membrane systems were investigated above and below the polymer transition temperature (37 and 25°C). Although the same cushion supported each lipid membrane, the polymer hydration profile and thickness were markedly different for DPPE and DPPC systems. Because DPPE and DPPC have different bending rigidities, these results establish that the polymer-membrane interaction is critically mediated by the mechanics of the membrane, providing better insight into cell-hydrogel interactions.     

An X-ray diffraction study of poly-L-homoarginine hydrochloride.

An X-ray study of the synthetic polypeptide poly(L -homoarginine hydrochloride) has been made to investigate whether, like the chemically related polypeptides poly(L -lysine hydrochloride), poly(L -arginine hydrochloride), and poly(L -ornithine hydrobromide), it can undergo conformational transitions merely from variations in its degree of hydration. X-ray photographs of powder and oriented specimens containing one to 15 molecules of water per L -homoarginine hydrochloride residue showed that this polymer forms only a β-pleated-sheet structure. The pleated sheets, formed by antiparallel polypeptide chains hydrogen-bonded to each other, are piled up along the b axis in an alternating sequence (“sandwich structure”). This structure did not appreciably change with variations of the degree of hydration, and the observed reflections at 56% relative humidity (1.8 molecules of water per residue) could be indexed satisfactorily in terms of a monoclinic unit cell, of space group P2₁, with a = 9.34 Å, b = 40.07 Å, c = 6.94 Å, and γ = 106°. These dimensions are shown by models to be compatible with the proposed structure, and the calculated density of 1.27 g/cm³ agrees well with the experimental value of 1.29 g/cm³. Removal of the last molecule of water results in a very diffuse pattern, while specimens containing 20 molecules of water per residue show only reflections due to water.     

不同水分处理对狗牙根种内相互作用的影响

以狗牙根当年生扦插苗为试验材料,根据库区河岸带水分特征设置4种水分处理方式:水分对照组(CK)、水淹与干旱交替组(FD)、土壤水分饱和组(LF)和全淹组(FL),4种密度方式:对照(1株/盆)、低密度(2株/盆)、中密度(4株/盆)及高密度(12株/盆),探究狗牙根生长及形态响应,并验证胁迫梯度假说。结果表明:(1)狗牙根各生物量随水分胁迫强度的增加显著下降(P0.001);密度处理和二者交互作用显著影响狗牙根叶干重、茎干重、根干重、地上生物量和总生物量(P0.001)。(2)水分处理显著影响狗牙根各形态指标(P0.001);密度和二者交互作用显著影响狗牙根分枝数、总茎长和节间长(P0.001)。(3)CK组和LF组狗牙根生物量相对邻体效应(RNE)均为负值,表明其种内关系为竞争关系。FL组各密度组生物量RNE值均为正值,其种内关系转化为促进关系。(4)中高密度组总茎长RNE值随水分胁迫增加而增大。研究表明:(1)狗牙根对不同的水分胁迫均表现出积极响应,可考虑将狗牙根用于库区河岸带植被重建。(2)随种植密度的增大,狗牙根生长及形态均表现出一定的负面效应。(3)本试验在一定程度上支持胁迫梯度假说,但尚需更多概念模型将其改进完善。     

Potentiometric and circular dichroic measurements of poly(L-glutamic acid) in aqueous solutions of organic and inorganic electrolytes at ambient temperature

Titration of an aqueous solution of sodium poly-L-glutamate with a strong acid usually produces turbidity and precipitation before the equivalence point is reached. In 1M sodium p-toluenesulfonate and 1M sodium methylcyclohexanesulfonate aggregation was delayed for days to months. In very concentrated tetra-n-butylammonium chloride and bromide the polymeric acid dissolved and could be titrated with NaOH. However, potentiometric titration curves in these solutions did not yield information (by way of plots of apparent pK versus the degree of neutralization) about the helix-to-coil transition of the polymer. It was argued in addition that the apparent pK of a weak polyelectrolyte should not be calculated from titrations in concentrated salt solutions since it is a mixed or composite quantity. It contains not only the effect of the salt on the dissociation of the weak electrolyte but its effect on the activity coefficient of hydrogen ions as well. Circular dichroic spectra were therefore measured a t various degrees of neutralization of poly(L -glutamic acid) in a number of aqueous salt solutions and mixtures of organic solvents with water. It was found that the undissociated polymer in the concentrated methylcyclohexanesulfonate and quaternary ammonium halide solutions had the spectrum of a right-handed α helix. The n → π* band at 222 mμ was used as a measure of the fraction of polymer in the helical conformation. The value of ? Δε for the undissociated polyacid in these organic electrolyte solutions was 11.4. By means of this value and a number of assumptions, the fraction of helix (f_h) as a function of α, the degree of polyacid neutralization, was calculated for the different solvent mixtures. An empirical equation was used to describe the variation of f_h with α, f_h = 1/(1 + e^?a+bα), in which b represents the degree of cooperativeness of the transition, and a is a measure of the effect of the medium on the onset of the transition. The values of b did not differ very much from one another, suggesting that the cooperativeness of the transition was not sensitive to changes in the medium. On the other hand, the value of a (or its equivalent, the value of α at the halfway point in the transition) was more dependent on the solvent. Comparisons of these results with those of some other workers were made by means of the empirical equation.     

Photolytic discoloration of azo dye incorporated organoiron polymer

Organoiron polymers with azo dyes pendant to the backbone incurred loss of color upon irradiation with UV light (λ = 300 nm) in acetonitrile solution. The loss of color is attributed to the interaction of the cleaved iron moiety with the azo chromophore. Similarly, addition of small amounts (⩽1 mM) of both Fe(II) and Fe(III) to the organic polymer analogue yielded comparable discoloration rates upon irradiation. The iron cation forms a complex with the azo chromophore group in the polymer, and subsequently leads to the photodegradation of the azo dye. At higher initial polymer concentrations, minimal discoloration was observed due to the light attenuation effect of the deeply colored solutions. In the presence of small amounts of water, the iron cation is inhibited from partaking in complex formation and no polymer discoloration was observed. For the organic polymer analogue, the presence of water did not show significant change over its absence upon irradiation. The discoloration of the polymer relies solely on its interaction with the iron cation present in solution, and does not require addition of any catalyst or reagent. This process might be developed into a pragmatic and viable method for the treatment of specifically designed colored materials using only UV light.     

Polymer-Grafted Liposomes: Physical Basis for the “Stealth” Property

Abstract

Polymer-bearing lipids have recently been incorporated into liposomes that are used in in vivo drug delivery. This strategy has improved the liposome's ability to avoid the reticuloendothelial system and has thereby increased its circulation time in the bloodstream. In order to understand the physical basis for this, so called, Stealth® effect, we have begun a series of studies that characterize the surface structure, interactive properties and in vivo performance of the polymer-bearing, Stealth lipids. For a 1900 g/mol polyethylene glycol (PEG) moiety, we have used x-ray diffraction and micropipet manipulation methods to show that, (i) the polymer chains extend ～50Å out from the lipid bilayer surface; (ii) this surface polymer exerts a significant long range mutual repulsion between adjacent bilayers that prevents bilayer-bilayer adhesion. Furthermore, the measured polymer extension and repulsive pressure are well modelled by polymer scaling laws. These results imply that the interaction of macromolecules and cellular surfaces with the Stealth liposome is probably limited to a distance of ～50Å from the liposome surface. We conclude that the origin of the Stealth effect lies in a steric stabilization mechanism. By using fluorescence video microscopy to observe implanted tumor tissue, we have also shown that fluorescent Stealth liposomes extravasate through the leaky vessel walls of tumors. This method allows us to characterize, in real time, the accumulation of liposomes and release of drug at an implanted tumor site.     

An X-ray diffraction study of poly(L-lysine hydrobromide)

A structural study of the synthetic polypeptide poly(L -lysine hydrobromide) has been made by X-ray fiber techniques. The investigation was undertaken to determine whelther this polymer undergoes conformational transitions as a function of hydration in a manner similar to other chemically related basic polypeptides. Specifically, a comparison with the previously reported structures of the hydrochloride form of poly(L -lysine) was sought. Homogeneous powder mixtures with various amounts of water and oriented fibers of poly(L -lysine hydrobromide) at different relative humidities were X-ray photographed. Reversible transitions amorphous state ? β-pleated sheet ? α-helix ? isotropic solution as a function of increasing/decreasing degrees of hydration were found. The β-pleated-sheet conformation was observed between 33% and 76% relative humidities (containing about one and three molecules of water per residue, respectively). Each pleated sheet was formed by “antiparallel” chains, and the sheets were piled up along the b-axis. The spacings of this conformation did not vary appreciably with hydration. The observed reflections at 52% relative humidity (1.4 molecules of water per residue) could be indexed satisfactorily in terms of an orthorhombic unit cell, of space group P2₁22₁, with a = 9.52 Å, b = 16.44 Å, and c = 6.80 Å. These dimensions were shown by models to be compatible with the proposed structure. The α-helix conformation was present in specimens photographed at 76% relative humidity and up, and containing between three and fifteen molecules of water per residue. The helices were packed parallel to each other in a hexagonal array but randomly along or about their lengths. Increasing the hydration from five to fifteen molecules of water per residue causes the a-axis to increase from 16.9 to 20.8 Å. Twenty molecules of water per residue produced an isotropic solution. Despite some structural differences between the hydrobromide and hydrochloride forms it is concluded that the role played by the anions is mainly related to determining the water content levels at which conformational changes occur. Therefore, the anions do not significantly influence the prevailing conformation in this particular system, but might affect the packing arrangement of the polypeptide chains.     

Synthesis and conformation of poly(L-lysyl-L-alanyl-L-alanyl), a sequence-ordered water-soluble copolymer

The sequence-ordered copolymer poly-(Lys-Ala-Ala) was synthesized by polycondensation of the N-hydroxysuccinimide ester of ε,Z-Lys-Ala-Ala and deprotection of the polymerization product. A fraction of molecular weight 13,000 obtained by ion-exchange chromatography was investigated. The polymer is freely soluble in water at all _pH values, and is completely digested by trypsin and elastase. From CD and ORD data it was concluded that in water at 1°C the ionized form (at _pH 6.5) of the polymer is helical. On heating, helix-coil transition curves were obtained with a midpoint, T_m, depending on salt concentration. In salt-free water T_m = 12.3°C and in 0.2M NaCl T_m = 28.5°C. Adding MeOH, causes an increase in the helical content of the polymer (half helicity at 20% MeOH, without salt, at 29°C). Guanidine·HCl was shown to decrease the helicity. At 1°C half helicity. The nonionized polymer helix is more stable (T_m～90°C). At the high pH, at 60°C, when concentration of the polymer is higher than 1.9 × 10^-2M, a precipitate is formed which redissolves on cooling with the original helicity. This does not occur in the presence of 50% MeOH. By comparison with polylysine it was concluded that replacing two-thirds of the lysine residues in polylysine by alanine leads to a polymer forming a more stable α-helix, when fully ionized. This is essentially due to the diminished coulombic repulsion. Uncharged lysine residues are comparable to alanine residues in their helix-forming tendency since the sequential polymer as well as one-third ionized polylysine are helical to approximately the same extent at room temperature.     

HRAS1 and LASS1 with APOE are associated with human longevity and healthy aging

The search for longevity‐determining genes in human has largely neglected the operation of genetic interactions. We have identified a novel combination of common variants of three genes that has a marked association with human lifespan and healthy aging. Subjects were recruited and stratified according to their genetically inferred ethnic affiliation to account for population structure. Haplotype analysis was performed in three candidate genes, and the haplotype combinations were tested for association with exceptional longevity. An HRAS1 haplotype enhanced the effect of an APOE haplotype on exceptional survival, and a LASS1 haplotype further augmented its magnitude. These results were replicated in a second population. A profile of healthy aging was developed using a deficit accumulation index, which showed that this combination of gene variants is associated with healthy aging. The variation in LASS1 is functional, causing enhanced expression of the gene, and it contributes to healthy aging and greater survival in the tenth decade of life. Thus, rare gene variants need not be invoked to explain complex traits such as aging; instead rare congruence of common gene variants readily fulfills this role. The interaction between the three genes described here suggests new models for cellular and molecular mechanisms underlying exceptional survival and healthy aging that involve lipotoxicity.     

Structure of a cellulose II-hydrazine complex

The structure of a crystalline cellulose II-hydrazine complex has been determined by x-ray diffraction methods as part of an investigation of cellulose-solvent interaction. The complex studied was that formed when Fortisan fibers were swollen in hydrazine and then vacuumdried. The unit cell is monoclinic with dimensions a = 9.37 Å, b = 19.88 Å, c = 10.39 Å, and γ = 120.0° and contains disaccharide segments of four chains, with one hydrazine per glucose residue. In view of the limited x-ray intensity data, the structure has been determined based on an approximate unit cell containing two chain segments, with a = 4.69 Å, using the linked-atom least-squares refinement procedures. The refined model contains antiparallel cellulose chains that are linked by both intermolecular hydrogen bonds and hydrogen-bonded hydrazine molecules. The parallel chains in the 020 planes are packed in register, leading to stacks of chains analogous to those in chitin. All the hydroxyl groups are satisfactorily hydrogen-bonded, and each hydrazine forms four donor and two acceptor hydrogen bonds, including an N? H…N bond between hydrazines. From this work it can be seen that the interaction of cellulose II with hydrazine involves scission of the intermolecular hydrogen bonds followed by disruption of the stacks of quarter-staggered chains. The latter effect is probably necessary for hydrazine to act as a cellulose solvent.     

Water Stress-Induced Changes in the Morphology of the Powdery Mildew, Leveillula taurica (Lèv.) Arn.

Water stress in Capsiucm annuum L., induced by means of polyethylene glycol influenced the length and branching frequency of conidiophores and conidial dimensions of the powdery mildew, Leveillula taurica (Lèv.) Arn. Conidiophore branching frequency and length as well as conidial length and width decreased with decreasing relative water content. The availability of water to host plants seems to have a direct effect on the growth vigour and development of the powdery mildew possibly is suggested that water stress may be imposed on host plants by the dry harmattan season resulting in reduced growth vigour of the powdery mildew. Morphology of powdery mildew developing under low water potential may be altered.     

Molecular dynamics simulation of drug uptake by polymer

Drug uptake by polymer was modeled using a molecular dynamics (MD) simulation technique. Three drugs—doxorubicin (water soluble), silymarin (sparingly water soluble) and gliclazide (water insoluble)—and six polymers with varied functional groups—alginic acid, sodium alginate, chitosan, Gantrez AN119 (methyl-vinyl–ether-co-malic acid based), Eudragit L100 and Eudragit RSPO (both acrylic acid based)—were selected for the study. The structures were modeled and minimized using molecular mechanics force field (MM+). MD simulation (Gromacs-forcefield, 300 ps, 300 K) of the drug in the vicinity of the polymer molecule in the presence of water molecules was performed, and the interaction energy (IE) between them was calculated. This energy was evaluated with respect to electric-dipole, van der Waals and hydrogen bond forces. A good linear correlation was observed between IE and our own previous data on drug uptake^* [R ² = 0.65, R_adj² = 0.65,R_pre² = 0.56, {\hbox{R}}_{\rm{adj}}^2 = 0.65,{\hbox{R}}_{\rm{pre}}^2 = 0.56, and a F ratio of 30.25, P < 0.001; Devarajan et al. (2005) J Biomed Nanotechnol 1:1–9]. Maximum drug uptake by the polymeric nanoparticles (NP) was achieved in water as the solvent environment. Hydrophilic interaction between NP and water was inversely correlated with drug uptake. The MD simulation method provides a reasonable approximation of drug uptake that will be useful in developing polymer-based drug delivery systems.