Nature of Subdiffusion Crossover in Molecular and Polymeric Glassformers

A crossover from a non-Gaussian to Gaussian subdiffusion has been observed ubiquitously in various polymeric and molecular glassformers. We have developed a framework that generalizes the fractional Brownian motion model to incorporate non-Gaussian features by introducing a jump kernel. We illustrate that the non-Gaussian fractional Brownian motion model accurately characterizes the subdiffusion crossover. From the solutions of the non-Gaussian fractional Brownian motion model, we gain insights into the nature of van Hove self-correlation in non-Gaussian subdiffusive regime, which is found to exhibit exponential tails, providing first such experimental evidence in molecular glassformers. The validity of the model is supported by comparison with incoherent quasielastic neutron scattering data obtained from several molecular and polymeric glassformers.

Modulation of Phase Behavior and Microscopic Dynamics in Cationic Vesicles by 1-Decyl-3-methylimidazolium Bromide

Synthetic cationic lipids have garnered significant attention as promising candidates for gene/DNA transfection in therapeutic applications. The phase behavior of the vesicles formed by these lipids is intriguing, revealing intricate connections to the structure and dynamics of the membrane. These phenomena emerge from the complex interplay between hydrophobic and electrostatic interactions of the lipids. In this study, we explore the impact of an ionic liquid-based surfactant, 1-decyl-3-methylimidazolium bromide (DMIM[Br]), on the structural, dynamical, and phase behavior of cationic dihexadecyldimethylammonium bromide (DHDAB) vesicles. Our investigations indicate that the addition of DMIM[Br] increases the vesicle size while thinning the membrane. Further, DMIM[Br] also induces substantial changes in the membrane phase behavior. At 10 and 25 mol %, DMIM[Br] eliminates the pre-transition from coagel to intermediate crystalline (IC) phase and decreases the onset temperature of the main phase transition to the fluid phase. In the cooling cycle, the addition of DMIM[Br] further induces the formation of an intermediate gel phase. This behavior is reminiscent of the non-synchronous ordering observed in the DODAB membrane, a longer-chain counterpart of DHDAB. Interestingly, at 40 mol % of DMIM[Br], the formation of the intermediate gel phase is largely suppressed. Neutron scattering data provide evidence that the addition of DMIM[Br] enhances lipid mobility in coagel and fluid phases, suggesting that DMIM[Br] acts as a plasticizer, enhancing membrane fluidity across all of the phases. Our findings infer that DMIM[Br] modulates the membrane's phase behavior and fluidity, two essential ingredients for the efficient transport of cargo, by controlling the balance of electrostatic and hydrophobic interactions.

Aspirin-Induced Ordering and Faster Dynamics of a Cationic Bilayer for Drug Encapsulation

The lipid dynamics and phase play decisive roles in drug encapsulation and delivery to the intracellular target. Thus, understanding the dynamic and structural alterations of membranes induced by drugs is essential for targeted delivery. To this end, united-atom molecular dynamics simulations of a model bilayer, dioctadecyldimethylammonium bromide (DODAB), are performed in the absence and presence of the usual nonsteroidal anti-inflammatory drug (NSAID), aspirin, at 298, 310, and 345 K. At 298 and 310 K, the bilayers are in the interdigitated two-dimensional square phases, which become rugged in the presence of aspirin, as evident from height fluctuations. At 345 K, the bilayer is in the fluid phase in both the absence and presence of aspirin. Aspirin is preferentially located near the oppositely charged headgroup and creates void space, which leads to an increase in the interdigitation and order parameters. Although the center of mass of lipids experiences structural arrest, they reach the diffusive regime faster and have higher lateral diffusion constants in the presence of aspirin. Results are found to be consistent with recent quasi-elastic neutron scattering studies that reveal that aspirin acts as a plasticizer and enhances lateral diffusion of lipids in both ordered and fluid phases. Different relaxation time scales of the bonds along the alkyl tails of DODAB due to the multitude of lipid motions become faster upon the addition of aspirin. Our results show that aspirin insertion is most favorable at physiological temperature. Thus, the ordered, more stable, and faster DODAB bilayer can be a potential drug carrier for the protected encapsulation of aspirin, followed by targeted and controlled drug release with antibacterial activity in the future.

Noncanonical Relationship between Heterogeneity and the Stokes-Einstein Breakdown in Deep Eutectic Solvents

The relationship between Stokes-Einstein breakdown (SEB) and dynamical heterogeneity (DH) is of paramount importance in the physical chemistry of complex fluids. In this work, we employ neutron scattering to probe the DH and SEB in a series of deep eutectic solvents (DESs) composed of acetamide and lithium salts. Quasielastic neutron scattering experiments reveal SEB in the jump diffusion of acetamide, represented by a fractional Stokes-Einstein relationship. Among these DESs, lithium perchlorate exhibits the most pronounced SEB while lithium bromide displays the weakest. Concurrently, elastic incoherent neutron scans identify that bromide DES is the most heterogeneous and perchlorate is the least. For the first time, our study unveils a counterintuitive incommensurate relationship between DH and SEB. Further, it reveals the intricate contrasting nature of the SEB-DH relationship when investigated in proximity to the glass-transition temperature and further away from it.

Modulation of Diffusion Mechanism and Its Correlation with Complexation in Aqueous Deep Eutectic Solvents

Aqueous mixtures of deep eutectic solvents (DESs) have gained traction recently as an effective template to tailor their physicochemical properties. But detailed microscopic insights into the effects of water on the molecular relaxation phenomenon in DESs are not entirely understood. DESs are strong network-forming liquids due to the extensive hydrogen bonding and complex formation between their species, and therefore, water can behave as a controlled disruptor altering the microscopic structure and dynamics in DESs. In this study, the role of water in the diffusion mechanism of acetamide in the aqueous mixtures of DESs synthesized using acetamide and lithium perchlorate is investigated using molecular dynamics (MD) simulation and quasielastic neutron scattering (QENS). The acetamide dynamics comprises localized diffusion within transient cages and a jump diffusion process across cages. The jump diffusion process is observed to be strongly enhanced by about a factor of 10 as the water content in the system is increased. Meanwhile, the geometry of the localized dynamics is unaltered by addition of water, but the localized diffusion becomes significantly faster and more heterogeneous with increasing water concentration. The accelerating effects of water on localized diffusion are also substantiated by QENS experiments. The water concentration in the DES is observed to control the solvation structure of lithium ions, with the ions becoming significantly hydrated at 20 wt % water. The formation of interwater and water-acetamide hydrogen bonds is observed. The increase in water concentration is found to increase the number of H-bonds; however, their lifetimes are found to decrease substantially. Similarly, the lifetimes of acetamide-lithium complexes are also found to be diminished by increasing water concentration. A power-law scaling relationship between lifetimes and diffusion constants is established, elucidating the extent of coupling between diffusive processes and hydrogen bonding and microscopic complexation. This study demonstrates the ability to use water as an agent to probe the role of structural relaxation and complex lifetimes of diffusive processes at different time and length scales.

Curcumin Accelerates the Lateral Motion of DPPC Membranes

Curcumin, the main ingredient in turmeric, has attracted attention due to its potential anti-inflammatory, anticancer, wound-healing, and antioxidant properties. Though curcumin efficacy is related to its interaction with biomembranes, there are few reports on the effects of curcumin on the lateral motion of lipids, a fundamental process in the cell membrane. Employing the quasielastic neutron scattering technique, we explore the effects of curcumin on the lateral diffusion of the dipalmotylphosphatidylcholine (DPPC) membrane. Our investigation is also supported by Fourier transform infrared spectroscopy, dynamic light scattering, and calorimetry to understand the interaction between curcumin and the DPPC membrane. It is found that curcumin significantly modulates the packing arrangement and conformations of DPPC lipid, leading to enhanced membrane dynamics. In particular, we find that the presence of curcumin substantially accelerates the DPPC lateral motion in both ordered and fluid phases. The effects are more pronounced in the ordered phase where the lateral diffusion coefficient increases by 23% in comparison to 9% in the fluid phase. Our measurements provide critical insights into molecular mechanisms underlying increased lateral diffusion. In contrast, the localized internal motions of DPPC are barely altered, except for a marginal enhancement observed in the ordered phase. In essence, these findings indicate that curcumin is favorably located at the membrane interface rather than in a transbilayer configuration. Further, the unambiguous evidence that curcumin modulates the membrane dynamics at a molecular level supports a possible action mechanism in which curcumin can act as an allosteric regulator of membrane functionality.

Can the microscopic and macroscopic transport phenomena in deep eutectic solvents be reconciled?

Deep eutectic solvents (DESs) have become ubiquitous in a variety of industrial and pharmaceutical applications since their discovery. However, the fundamental understanding of their physicochemical properties and their emergence from the microscopic features is still being explored fervently. Particularly, the knowledge of transport mechanisms in DESs is essential to tune their properties, which shall aid in expanding the territory of their applications. This perspective presents the current state of understanding of the bulk/macroscopic transport properties and microscopic relaxation processes in DESs. The dependence of these properties on the components and composition of the DES is explored, highlighting the role of hydrogen bonding (H-bonding) interactions. Modulation of these interactions by water and other additives, and their subsequent effect on the transport mechanisms, is also discussed. Various models (e.g. hole theory, free volume theory, etc.) have been proposed to explain the macroscopic transport phenomena from a microscopic origin. But the formation of H-bond networks and clusters in the DES reveals the insufficiency of these models, and establishes an antecedent for dynamic heterogeneity. Even significantly above the glass transition, the microscopic relaxation processes in DESs are rife with temporal and spatial heterogeneity, which causes a substantial decoupling between the viscosity and microscopic diffusion processes. However, we propose that a thorough understanding of the structural relaxation associated to the H-bond dynamics in DESs will provide the necessary framework to interpret the emergence of bulk transport properties from their microscopic counterparts.

Water accelerates the hydrogen-bond dynamics and abates heterogeneity in deep eutectic solvent based on acetamide and lithium perchlorate

Deep eutectic solvents (DESs) have become a prevalent and promising medium in various industrial applications. The addition of water to DESs has attracted a lot of attention as a scheme to modulate their functionalities and improve their physicochemical properties. In this work, we study the effects of water on an acetamide based DES by probing its microscopic structure and dynamics using classical molecular dynamics simulation. It is observed that, at low water content, acetamide still remains the dominant solvate in the first solvation shell of lithium ions, however, beyond 10 wt. %, it is replaced by water. The increase in the water content in the solvent accelerates the H-bond dynamics by drastically decreasing the lifetimes of acetamide-lithium H-bond complexes. Additionally, water-lithium H-bond complexes are also found to form, with systematically longer lifetimes in comparison to acetamide-lithium complexes. Consequently, the diffusivity and ionic conductivity of all the species in the DES are found to increase substantially. Non-Gaussianity parameters for translational motions of acetamide and water in the DES show a conspicuous decrease with addition of water in the system. The signature of jump-like reorientation of acetamide is observed in the DES by quantifying the deviation from rotational Brownian motion. However, a notable decrease in the deviation is observed with an increase in the water content in the DES. This study demonstrates the intricate connection between H-bond dynamics and various microscopic dynamical parameters in the DES, by investigating the modulation of the former with addition of water.

Dioctadecyldimethylammonium bromide, a surfactant model for the cell membrane: Importance of microscopic dynamics

Cationic lipid membranes have recently attracted huge attention both from a fundamental point of view and due to their practical applications in drug delivery and gene therapy. The dynamical behavior of the lipids in the membrane is a key parameter controlling various physiological processes and drug release kinetics. Here, we review the dynamical and thermotropic phase behavior of an archetypal cationic lipid membrane, dioctadecyldimethylammonium bromide (DODAB), as studied using neutron scattering and molecular dynamics simulation techniques. DODAB membranes exhibit interesting phase behavior, specifically showing coagel, gel, and fluid phases in addition to a large hysteresis when comparing heating and cooling cycles. The dynamics of the lipid membrane is strongly dependent on the physical state of the bilayer. Lateral diffusion of the lipids is faster, by an order of magnitude, in the fluid phase than in the ordered phase. It is not only the characteristic times but also the nature of the segmental motions that differ between the ordered and fluid phases. The effect of different membrane active molecules including drugs, stimulants, gemini surfactants, and unsaturated lipids, on the dynamical and thermotropic phase behavior of the DODAB membrane, is also discussed here. Various interesting features such as induced synchronous ordering between polar head groups and tails, sub diffusive behavior, etc., are observed. The results shed light on the interaction between these additives and the membrane, which is found to be a complex interplay between the physical state of the membrane, charge, concentration, molecular architecture of the additives, and their location within the membrane.

Effects of NSAIDs on the Dynamics and Phase Behavior of DODAB Bilayers

Despite well-known side effects, nonsteroidal anti-inflammatory drugs (NSAIDs) are one of the most prescribed drugs worldwide for their anti-inflammatory and antipyretic properties. Here, we report the effects of two NSAIDs, aspirin and indomethacin, on the thermotropic phase behavior and the dynamics of a dioctadecyldimethylammonium bromide (DODAB) lipid bilayer as studied using neutron scattering techniques. Elastic fixed window scans showed that the addition of aspirin and indomethacin affects the phase behavior of a DODAB bilayer in both heating and cooling cycles. Upon heating, there is a change in the coagel- to fluid-phase transition temperature from 327 K for pure DODAB bilayer to 321 and 323 K in the presence of aspirin and indomethacin, respectively. More strikingly, upon cooling, the addition of NSAIDs suppresses the formation of the intermediate gel phase observed in pure DODAB. The suppression of the gel phase on addition of the NSAIDs evidences the synchronous ordering of a lipid headgroup and chain. Analysis of quasi-elastic neutron scattering data showed that only localized internal motion exists in the coagel phase, whereas both internal and lateral motions exist in the fluid phase. The internal motion is described by a fractional uniaxial rotational diffusion model in the coagel phase and by a localized translation diffusion model in the fluid phase. In the coagel phase, the rotational diffusion coefficient of DODAB is found to be almost twice for the addition of the drugs, whereas the mobility fraction did not change for indomethacin but becomes twice for aspirin. In the fluid phase, the lateral motion, described well by a continuous diffusion model, is found to be slower by about ∼30% for indomethacin but almost no change for aspirin. For the internal motion, addition of aspirin leads to enhancement of the internal motion, whereas indomethacin did not show significant effect. This study shows that the effect of different NSAIDs on the dynamics of the lipid membrane is not the same; hence, one must consider these NSAIDs individually while studying their action mechanism on the cell membrane.

Effects of Hydrotropic Salt on the Nanoscopic Dynamics of DTAB Micelles

Effects of a hydrotropic salt, sodium salicylate (NaSal), on the dynamic behavior of cationic dodecyltrimethylammonium bromide (DTAB) micelles as studied using dynamic light scattering (DLS) and quasielastic neutron scattering (QENS) techniques are reported here. DLS study showed that the addition of NaSal leads to a decrease in the apparent diffusion coefficient of the whole micelle indicating micellar growth. QENS data analysis suggested that observed dynamics involves two distinct motions, lateral motion of the surfactant over the curved micellar surface and localized segmental motion of the surfactant. It is found that the addition of NaSal slows down the lateral motion of DTAB while the localized segmental motion of the DTAB chain is not affected much. An atomistic molecular dynamics (MD) simulation was performed to gain further insight into the underlying phenomena. MD simulation results are found to be consistent with the experimental observations. MD simulation revealed that location of the salicylate ions on the micellar surface and their strong electrostatic association with their oppositely charged surfactant headgroup are the major factors in slowing down the lateral motion of the DTAB molecule. In the present work, a quantitative description of the effects of NaSal on the nanoscopic dynamics of DTAB micelles and its correlation with the microstructure of the micelle is provided.

Plasma protein analysis of patients with different B-cell lymphomas using high-content antibody microarrays

PURPOSE

In this study, plasma samples from a multicentric case-control study on lymphoma were analyzed for the identification of proteins useful for diagnosis.

EXPERIMENTAL DESIGN

The protein content in the plasma of 100 patients suffering from the three most common B-cell lymphomas and 100 control samples was studied with antibody microarrays composed of 810 antibodies that target cancer-associated proteins. Sample pools were screened for an identification of marker proteins. Then, the samples were analyzed individually to validate the usability of these markers.

RESULTS

More than 200 proteins with disease-associated abundance changes were found. The evaluation on individual patients confirmed some molecules as robust informative markers while others were inadequate for this purpose. In addition, the analysis revealed distinct subgroups for each of the three investigated B-cell lymphoma subtypes. With this information, we delineated a classifier that discriminates the different lymphoma entities.

CONCLUSIONS AND CLINICAL RELEVANCE

Variations in plasma protein abundance permit discrimination between different patient groups. After validation on a larger study cohort, the findings could have diagnostic as well as differential diagnostic potential. Beside this, methodological aspects were critically evaluated, such as the value of sample pooling for the identification of biomarkers that are useful for a diagnosis on individual patients.

Verrucous carcinoma in association with oral submucous fibrosis

Oral verrucous carcinoma is a form of well differentiated squamous cell carcinoma characterized by exophytic over growth. It is slow growing and locally invasive tumor occurring in 6 th and 7 th decade of life. Smoking and chewing tobacco is found to be the most common etiological factor of verrucous carcinoma although oral leukoplakia may act as a predisposing factor. This is a rare case of oral verrucous carcinoma seen in association with oral submucous fibrosis in a younger patient with long standing history of chewing tobacco.

Algorithms as guides for the prevention of permanent nerve damage in leprosy patients

The responsibility for treating leprosy patients is being passed on to the general medical and health care services, predominantly located in primary health care centres. It therefore becomes necessary for the staff of these services to have clear guidelines on what they should do to prevent permanent nerve damage and its consequences when they come across a leprosy patient with neuritis or nerve function deficit. Six algorithms to help achieve this purpose are presented in this article.

Location of Impaired Sensory Conduction of the Median Nerve in Carpal Tunnel Syndrome

Sensory conduction of the median nerve at the carpal tunnel for eight consecutive 1 cm segments of the nerve was evaluated in 217 hands of 153 of our patients with carpal tunnel syndrome. Impairment was found to be highly focal and often confined to a single 1 cm segment of the nerve. The section of the nerve at or just distal to the distal margin of the carpal tunnel was affected most frequently, the section within the tunnel was affected less often, and the section proximal to the tunnel at the level of the mid-carpal and radio-carpal joints was affected least. The greatest contrast between frequencies of slowing at adjacent segments occurred at the proximal and distal margins of the carpal tunnel. The distribution of the nerve impairment was similar between the sexes; however, among the men the segment affected most frequently was located 1 cm distal to the segment affected most frequently among the women. The general pattern of slowing which we found does not substantiate some commonly-held opinions about the aetiology of carpal tunnel syndrome.

Do we need trials of agents alleged to improve healing of plantar ulcers?

The assumptions underlying trials of agents claiming to heal plantar ulcers 'faster' and 'better' are shown to be fallacious and it is pointed out that in most cases these ulcers fail to heal for lack of attention and not for want of a specific topical agent. Clinical trials in this area are difficult and are not worth the trouble as they do not add to our knowledge about these ulcers or their management in the clinic or in the field.

Value of thermal sensibility testing in leprosy diagnosis in the field--field trial of a pocket device

A handy thermal sensibility testing device has been developed and field tested in different centres in Africa and India. The device performed satisfactorily under field conditions and made testing for thermal sensibility in the field practicable and easy. Examination of the results of testing 260 persons, most of them having a few lesions of early leprosy, showed that the expected increase in the rate of diagnosis of sensory impairment in the skin lesions, and so in the diagnosis of leprosy, would be about 15-25% when thermal sensibility testing using this device was added to the other sensibility tests routinely used in the field. Regular use of this device in the field will help to bring more leprosy patients under treatment than at present.

Leprosy diagnosis: a device for testing the thermal sensibility of skin lesions in the field

A handy device for testing the thermal sensibility of skin lesions has been developed and field tested in various centres in Africa and India. The instrument performed satisfactorily and its use made testing for thermal sensibility in the field practicable and straightforward. Analysis of the results of testing 260 persons, most of whom exhibited a few lesions that were characteristic of early leprosy, showed that the rate of diagnosis of sensory impairment of such skin lesions, and hence the diagnosis of leprosy, would be about 15-25% more if thermal sensibility testing using this device were added to the other tests of sensibility routinely carried out in the field. Regular use of the device in the field would help to bring more leprosy patients under treatment than at present.

Antibodies to HIV-1 in sera from patients with mycobacterial infections

Sera from 478 persons (348 leprosy patients, 33 tuberculosis patients, 29 healthy contacts of leprosy patients, 38 normal healthy Indians, and 30 normal healthy Europeans) were screened for anti-HIV-1 IgG antibodies by ELISA. None was positive. In addition, 132 samples (from 43 leprosy patients, 21 tuberculosis patients, 5 healthy contacts of leprosy patients, 33 normal healthy Indians, and 30 normal healthy Europeans) were also tested by Western blot assay for anti-HIV-1 IgG antibodies. Only 1 of the 63 healthy subjects expressed a prominent p17 band. One or more bands were found in 44 (leprosy patients 33/43, tuberculosis patients 7/21, and leprosy contacts 4/5) of the remaining 69 sera. Antibody to the HIV-1-specific antigen p24 was expressed by 17 of these subjects (14/43 leprosy patients, 1/21 tuberculosis patients, and 2/5 leprosy contacts), either as a single band or in combination with other bands. This raises the possibility of a common antigenic pattern between HIV-1 and mycobacteria, especially Mycobacterium leprae.

Secondary and primary dapsone resistant leprosy: an analysis of 199 patients from St. Thomas Hospital and leprosy project, Chettupattu, South India

The occurrence of secondary and primary dapsone resistance in 199 patients in our control area and the influence of certain variables such as age, initial bacteriological and morphological indices, duration of regular dapsone monotherapy, on the emergence of dapsone resistance was investigated. Ninety one of 122 patients and 29 out of 77 showed secondary (SDR) and primary (PDR) resistance to dapsone respectively. Very low BI (BI:2.5) group also showed both SDR (60%) and PDR (40%). Low or high MI group exhibited the same degree of resistance. Multiplication of M. leprae was obtained even when the MI of the inocula was zero. Even in the group who had 1 to 5 years duration of regular dapsone treatment, 85% patients showed SDR. Significance of such results are discussed in relation to chemotherapy. The overall minimum prevalence of SDR was found to be 5.6% and 21% in the case of PDR in our control area.

Foot pressure measurement in leprosy and footwear design

Leprosy patients deprived of sensory feedback allow excessive pressures to be applied to feet, thereby cause foot ulcers. Quantitative knowledge of the pressure distribution under leprotic feet is helpful to prevent further damage to foot by designing suitable footwear. This paper describes barographic technique for measurement of pressures under the leprotic feet and the design of special footwear for prevention of foot ulcers.

Dermadesis and flexor pulley advancement: first report on a simple operation for correction of paralytic claw fingers in patients with leprosy

A simple operation is described for correcting the intrinsic minus finger deformity commonly seen in patients with leprosy. It consists of shortening the palmar skin at the level of the MP joint and flexor pulley advancement. This produces an acceptable flexion contracture of not more than 40 degrees of the MP joint, as in Zancolli's capsuloplasty, and optimizes the balance of forces around the finger joints in favor of improved MP joint flexion and PIP joint extension. A preliminary evaluation of 11 hands of patients with leprosy with ulnar or ulnar and median nerve paralysis who underwent this surgery and were followed for 7 to 17 months after surgery shows that this operation satisfactorily corrects claw deformity and improves intrinsic minus disability. The most important advantages of this procedure are that it is technically simple and does not require postoperative reeducative therapy.