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ABSTRACT At the MRS Fall 2014 Meeting, Symposium E, we reported on morphologies, fragmentation, and hardness in synthetic hydrogen urate monohydrate (monosodium urate monohydrate, MSUM, or MSU) crystals. We are now presenting further... more
ABSTRACT At the MRS Fall 2014 Meeting, Symposium E, we reported on morphologies, fragmentation, and hardness in synthetic hydrogen urate monohydrate (monosodium urate monohydrate, MSUM, or MSU) crystals. We are now presenting further characterization results, including some from the biomaterial that forms in humans with gout disease: The fanning of radiating blades (needles) in spherulitic grains of synthetic MSUM was examined by microscopy techniques. These and previous data are consistent with an interpretation in terms of the crystallographic parameters in the unit cell, and the presence of dislocation arrays at low angle boundaries. The kinetics of such branched growth is here related to thermodynamic properties and super-saturation levels. Secondary nucleation is an additional mechanism leading to more complex morphologies. Differences in overall growth rates, under conditions of either branched or single needle growth, are considered in relation to gout. Novel powder XRD and solid state NMR data show, respectively, preferred orientation in the biomaterial, and the potential of NMR for identifying and characterizing MSUM in specific environments, helping to resolve pending questions in gout. Present results are anticipated to be useful for designing bio-inspired and bio-mimetic materials, regarding morphologies, overall growth rates, and mechanical properties.
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A major challenge in liposomal research is to minimize the leakage of encapsulated cargo from either uncontrolled passive permeability across the liposomal membrane or upon fusion with other membranes. We previously showed that liposomes... more
A major challenge in liposomal research is to minimize the leakage of encapsulated cargo from either uncontrolled passive permeability across the liposomal membrane or upon fusion with other membranes. We previously showed that liposomes made from pure Archaea-inspired bipolar tetraether lipids exhibit exceptionally low permeability of encapsulated small molecules due to their capability to form more tightly packed membranes compared to typical monopolar lipids. Here, we demonstrate that liposomes made of synthetic bipolar tetraether lipids can also undergo membrane fusion, which is commonly accompanied by content leakage of liposomes when using typical bilayer-forming lipids. Importantly, we demonstrate calcium-mediated fusion events between liposome made of glycerolmonoalkyl glycerol tetraether lipids with phosphatidic acid headgroups (GMGTPA) occur without liposome content release, which contrasts with liposomes made of bilayer-forming EggPA lipids that displayed ~80% of content ...
Restricted rotation through tethering of lipids as found in archaea helps maintain barrier function at elevated temperatures.
Guest dynamics inside pyrogallol[4]arene hexamers in the solid state are sensitive to structure external to the host.
Ball milling mixtures of pyrogallol[4]arene and guests gives direct access to encapsulation complexes and can be monitored by solid-state NMR.
The molecular interactions of silk materials plasticized using glycerol were studied, as these materials provide options for biodegradable and flexible protein-based systems. Plasticizer interactions with silk were analyzed by thermal,... more
The molecular interactions of silk materials plasticized using glycerol were studied, as these materials provide options for biodegradable and flexible protein-based systems. Plasticizer interactions with silk were analyzed by thermal, spectroscopic, and solid-state NMR analyses. Spectroscopic analysis implied that glycerol was hydrogen bonded to the peptide matrix, but may be displaced with polar solvents. Solid-state NMR indicated that glycerol induced β-sheet formation in the dried silk materials, but not to the extent of methanol treatment. Fast scanning calorimetry suggested that β-sheet crystal formation in silk-glycerol films appeared to be less organized than in the methanol treated silk films. We propose that glycerol may be simultaneously inducing and interfering with β-sheet formation in silk materials, causing some improper folding that results in less-organized silk II structures even after the glycerol is removed. This difference, along with trace residual glycerol, al...
ABSTRACTTo achieve the goal of biocompatibility in nano-based materials we must first obtain a fundamental understanding of the physical and chemical behavior of biomolecules at the interfaces of nanomaterials. A first step towards... more
ABSTRACTTo achieve the goal of biocompatibility in nano-based materials we must first obtain a fundamental understanding of the physical and chemical behavior of biomolecules at the interfaces of nanomaterials. A first step towards understanding protein interactions with nanomaterials is to understand how individual amino acids interact at the interfaces. In this paper, we investigated the lysine adsorption behavior on fumed silica nanoparticles by solid-state NMR spectroscopy. We use1H,13C and15N solid-state magic angle spinning (MAS) NMR techniques to elucidate how lysine is adsorbed on silica nanoparticles surfaces via strong hydrogen-bonding interaction between the protonated side-chain amine group and silanol group on silica nanoparticles surfaces.*
This paper examines the effects of four different polar headgroups on small-ion membrane permeability from liposomes comprised of Archaea-inspired glycerolmonoalkyl glycerol tetraether (GMGT) lipids. We found that the membrane-leakage... more
This paper examines the effects of four different polar headgroups on small-ion membrane permeability from liposomes comprised of Archaea-inspired glycerolmonoalkyl glycerol tetraether (GMGT) lipids. We found that the membrane-leakage rate across GMGT lipid membranes varied by a factor of ≤1.6 as a function of headgroup structure. However, the leakage rates of small ions across membranes comprised of commercial bilayer-forming 1-palmitoyl-2-oleoyl-sn-glycerol (PO) lipids varied by as much as 32-fold within the same series of headgroups. These results demonstrate that membrane leakage from GMGT lipids is less influenced by headgroup structure, making it possible to tailor the structure of the polar headgroups on GMGT lipids while retaining predictable leakage properties of membranes comprised of these tethered lipids.
Investigating the interface between biomolecules and nanoparticles has attracted considerable attention in recent years since it has great significance in numerous fields including nanotechnology, biomineralization, cancer therapy, and... more
Investigating the interface between biomolecules and nanoparticles has attracted considerable attention in recent years since it has great significance in numerous fields including nanotechnology, biomineralization, cancer therapy, and origin of life. In this paper, we present a thorough solid-state NMR study on alanine adsorption and thermal condensation on fumed silica nanoparticles. The structure and dynamics at the interface between alanine and fumed silica nanoparticles were probed with a combination of 1H, 13C, and 15N one- and two-dimensional (2D) magic angle spinning (MAS) solid-state NMR methods at different alanine surface coverages and hydration levels. It is illustrated at high surface coverages both crystalline and adsorbed states of alanine exist in the samples while only adsorbed alanine is observed at low surface coverage (approximately a monolayer). At high hydration levels, the adsorbed alanine exhibits enhanced mobility, and both the carboxyl and amine group interact with mobile water m...
Extremophile archaeal organisms overcome problems of membrane permeability by producing lipids with structural elements that putatively improve membrane integrity compared to lipids from other life forms. Herein, we describe a series of... more
Extremophile archaeal organisms overcome problems of membrane permeability by producing lipids with structural elements that putatively improve membrane integrity compared to lipids from other life forms. Herein, we describe a series of lipids that mimic some key structural features of archaeal lipids, such as: 1) single tethering of lipid tails to create fully transmembrane tetraether lipids and 2) the incorporation of small rings into these tethered segments. We found that membranes formed from pure tetraether lipids leaked small ions at a rate that was about two orders of magnitude slower than common bilayer‐forming lipids. Incorporation of cyclopentane rings into the tetraether lipids did not affect membrane leakage, whereas a cyclohexane ring reduced leakage by an additional 40 %. These results show that mimicking certain structural features of natural archaeal lipids results in improved membrane integrity, which may help overcome limitations of many current lipid‐based technol...
We report that supramolecular polymer films composed of a 2:1 mixture of monodiamidopyridine diketopyrrolopyrrole (DPP) electron donors and perylene bisdiimide (PDI) electron acceptors undergo photoinduced charge transfer in the solid... more
We report that supramolecular polymer films composed of a 2:1 mixture of monodiamidopyridine diketopyrrolopyrrole (DPP) electron donors and perylene bisdiimide (PDI) electron acceptors undergo photoinduced charge transfer in the solid state. Film formation is guided by complementary noncovalent interactions programmed into the molecular components, resulting in a film architecture comprised of polymer wires with order across the molecular-to-macroscopic continuum. Using ultrafast transient absorption spectroscopy, we show that recombination lifetimes increase 1000-fold compared to the same supramolecular polymers in solution. Supramolecular donor–acceptor polymer films, such as these, that are designed by considering structure and electron transfer dynamics synergistically could lead to breakthroughs in organic optoelectronics.
In this work, thermal condensation of alanine adsorbed on fumed silica nanoparticles is investigated using thermal analysis and multiple spectroscopic techniques including infrared (IR), Raman and nuclear magnetic resonance (NMR)... more
In this work, thermal condensation of alanine adsorbed on fumed silica nanoparticles is investigated using thermal analysis and multiple spectroscopic techniques including infrared (IR), Raman and nuclear magnetic resonance (NMR) spectroscopies. Thermal analysis shows that adsorbed alanine can undergo thermal condensation forming peptide bonds within a short time period and at a lower temperature (~170 °C) on fumed silica nanoparticle surfaces than that in bulk (~210 °C). Spectroscopic results further show that alanine is converted to alanine anhydride with a yield of 98.8 % during thermal condensation. After comparing peptide formation on solution-derived colloidal silica nanoparticles, it is found that fumed silica nanoparticles show much better efficiency and selectivity than solution-derived colloidal silica nanoparticles for synthesizing alanine anhydride. Furthermore, Raman spectroscopy provides evidence that the high efficiency for fumed silica nanoparticles is likely related to their unique surface features: the intrinsic high population of strained ring structures present at the surface. This work indicates the great potential of fumed silica nanoparticles in synthesizing peptides with high efficiency and selectivity.
Solid-state NMR and molecular dynamics (MD) simulations are presented to help elucidate the molecular secondary structure of poly(Gly-Gly-X), which is one of the most common structural repetitive motifs found in orb-weaving dragline... more
Solid-state NMR and molecular dynamics (MD) simulations are presented to help elucidate the molecular secondary structure of poly(Gly-Gly-X), which is one of the most common structural repetitive motifs found in orb-weaving dragline spider silk proteins. The combination of NMR and computational experiments provides insight into the molecular secondary structure of poly(Gly-Gly-X) segments and provides further support that these regions are disordered and primarily non-β-sheet. Furthermore, the combination of NMR and MD simulations illustrate the possibility for several secondary structural elements in the poly(Gly-Gly-X) regions of dragline silks, including β-turns, 310-helicies, and coil structures with a negligible population of α-helix observed.
Spider silk is nature's super biopolymer with unsurpassed mechanical properties combining a strength comparable to Kevlar and an extensibility that surpasses nylon. Dragline silk is made of two proteins: Major ampullate spidroin 1 and... more
Spider silk is nature's super biopolymer with unsurpassed mechanical properties combining a strength comparable to Kevlar and an extensibility that surpasses nylon. Dragline silk is made of two proteins: Major ampullate spidroin 1 and 2 (MaSp1 and MaSp2) and has been described as a co-biopolymer. A better understanding of the molecular conformation of the proteins and how this correlates to the mechanical properties of the silk is needed. To date, most of the structural characterization of spider silk has been on the Nephila species that has a MaSp1:MaSp2 ratio of 80:20. MaSp2 has a high proline content that has been correlated to a number of interesting properties such as elasticity and supercontraction is spider silks. Although β-spirals and turn-like secondary structures have been proposed for the proline-rich GPGXX motif in MaSp2, experimental evidence is lacking to prove these structural arrangements. The Argiopes species produces silk that contains a larger percentage of M...
The molecular dynamics of the proteins that comprise spider dragline silk were investigated with solid-state (2)H magic angle spinning (MAS) NMR line shape and spin-lattice relaxation time (T1) analysis. The experiments were performed on... more
The molecular dynamics of the proteins that comprise spider dragline silk were investigated with solid-state (2)H magic angle spinning (MAS) NMR line shape and spin-lattice relaxation time (T1) analysis. The experiments were performed on (2)H/(13)C/(15)N-enriched N. clavipes dragline silk fibers. The silk protein side-chain and backbone dynamics were probed for Ala-rich regions (β-sheet and 31-helical domains) in both native (dry) and supercontracted (wet) spider silk. In native (dry) silk fibers, the side chains in all Ala containing regions undergo similar fast methyl rotations (>10(9) s(-1)), while the backbone remains essentially static (<10(2) s(-1)). When the silk is wet and supercontracted, the presence of water initiates fast side-chain and backbone motions for a fraction of the β-sheet region and 31-helicies. β-Sheet subregion 1 ascribed to the poly(Ala) core exhibits slower dynamics, while β-sheet subregion 2 present in the interfacial, primarily poly(Gly-Ala) region...
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ABSTRACT Hydrogen-bonding plays a key role in the structure and dynamics of a wide range of materials from small molecules to complex biomolecules. 1H NMR has emerged as a powerful tool for studying hydrogen-bonding because the proton... more
ABSTRACT Hydrogen-bonding plays a key role in the structure and dynamics of a wide range of materials from small molecules to complex biomolecules. 1H NMR has emerged as a powerful tool for studying hydrogen-bonding because the proton isotropic chemical shift exhibits a dependence on the interatomic distances associated with the hydrogen bond. In the present work, we illustrate the use of ultrafast magic angle spinning at high magnetic field (800 MHz) for resolving multiple hydrogen-bonding sites in a set of crystalline phosphonic acids that contain various functional groups (−COOH, −PO3H2, and −NH3+). Trends are observed between the proton chemical shift of the hydrogen-bonded proton and the associated hydrogen-bonding distances (O–H···X) from X-ray crystallography. Density functional theory calculations conducted on the phosphonic acid structures illustrate that the experimental proton chemical shift dependence on hydrogen-bond distance agrees with the expected theoretical trends. Further, it is shown that the chemical shift trend varies considerably depending on the functional group participating in the hydrogen bonding, albeit a −COOH, −PO3H2, or −NH3+ moiety. An improved understanding of these trends for various functional groups should be useful for determining accurate hydrogen-bond strengths from the proton chemical shift in an array of systems.
... GP Holland,* BR Cherry, and TM Alam. Department of Biomolecular and Chemical Analysis, Sandia National Laboratories, Albuquerque, New Mexico 87185. J. Phys. Chem. B , 2004, 108 (42), pp 16420–16426. DOI: 10.1021 ...
ABSTRACT Spider silks display some of the most impressive mechanical properties of known fibrous materials. However, a molecular level understanding of how spiders store and convert the highly concentrated protein-rich fluid in the gland... more
ABSTRACT Spider silks display some of the most impressive mechanical properties of known fibrous materials. However, a molecular level understanding of how spiders store and convert the highly concentrated protein-rich fluid in the gland to an insoluble super fiber at the spinneret remains unanswered. In this report, we demonstrate the utility of High-Resolution Magic Angle Spinning (HR-MAS) NMR spectroscopy to study the molecular structure of the proteins within excised major ampullate (MA) glands from two orb weaving spiders, Nephila clavipes and Argiope aurantia. The spiders were fed various 13 C-enriched amino acids to target different regions of the proteins and enable multi-dimensional, multinuclear HR-MAS NMR experiments. Comparisons are made between these HR-MAS results on MA glands and previous solid-state NMR data on spider dragline silk. The conformation-dependent 13 C and 1 H isotropic chemical shifts obtained in this study indicate that both dragline silk proteins, major ampullate spidroin 1 (MaSp1) and 2 (MaSp2), are present in a random coil conformation in the MA gland prior to fiber formation for both spider species.
ABSTRACT An overview of solid-state NMR structural studies on various silk forms and analogs conducted by the authors' research groups is presented. The well-studied silkworm and spider silks together with related silk peptides... more
ABSTRACT An overview of solid-state NMR structural studies on various silk forms and analogs conducted by the authors' research groups is presented. The well-studied silkworm and spider silks together with related silk peptides have a mixture of secondary structures including β-sheet, β-turn, helix and random coil that are difficult to analyze by X-ray diffraction and electron microscopy but conveniently investigated by solid-state NMR. Several newly developed solid-state NMR techniques and stable isotope labeling approaches of the silks were effectively used to characterize silk structure. The techniques discussed provide not only information on the secondary structure, but also on the hydrogen-bonding interactions present in the silks. Structural studies on other types of silk, silk peptide mimics and recombinant silk proteins are also discussed.
ABSTRACT The application of native silk and recombinant silk as biomaterials is a particularly active area. Silk is an attractive biomaterial because of its excellent mechanical properties, that is, the combination of strength and... more
ABSTRACT The application of native silk and recombinant silk as biomaterials is a particularly active area. Silk is an attractive biomaterial because of its excellent mechanical properties, that is, the combination of strength and toughness not found in today's man-made materials together with its excellent biocompatibility. The well-developed X-ray diffraction technique was expected to clarify the atomic level structure, but the analysis cannot be used for this purpose because it is difficult to obtain the single crystals that are required to solve the complete molecular structure of silk. The works about B. mori silk fibroin structure before and after spinning were published from Asakura's group. Rotational-Echo Double Resonance is a commonly used ssNMR method for determining conformations in biopolymers through quantitative distance determination.
Carbonaceous chondrites are asteroidal meteorites that contain abundant organic materials. Given that meteorites and comets have reached the Earth since it formed, it has been proposed that the exogenous influx from these bodies provided... more
Carbonaceous chondrites are asteroidal meteorites that contain abundant organic materials. Given that meteorites and comets have reached the Earth since it formed, it has been proposed that the exogenous influx from these bodies provided the organic inventories necessary for the emergence of life. The carbonaceous meteorites of the Renazzo-type family (CR) have recently revealed a composition that is particularly enriched in small soluble organic molecules, such as the amino acids glycine and alanine, which could support this possibility. We have now analyzed the insoluble and the largest organic component of the CR2 Grave Nunataks (GRA) 95229 meteorite and found it to be of more primitive composition than in other meteorites and to release abundant free ammonia upon hydrothermal treatment. The findings appear to trace CR2 meteorites’ origin to cosmochemical regimes where ammonia was pervasive, and we speculate that their delivery to the early Earth could have fostered prebiotic mol...
Significance The data reported here suggest a far larger availability of meteoritic organic materials for planetary environments than previously assumed and that molecular evolution on the early Earth could have benefited from accretion... more
Significance The data reported here suggest a far larger availability of meteoritic organic materials for planetary environments than previously assumed and that molecular evolution on the early Earth could have benefited from accretion of carbonaceous meteorites both directly with soluble compounds and, for a more protracted time, through alteration, processing, and release from their insoluble organic materials.
The effect of a distribution in the (1)H-(1)H dipolar coupling on (1)H double-quantum (DQ) magic angle spinning (MAS) nuclear magnetic resonance (NMR) spinning sideband patterns is considered. In disordered or amorphous materials a... more
The effect of a distribution in the (1)H-(1)H dipolar coupling on (1)H double-quantum (DQ) magic angle spinning (MAS) nuclear magnetic resonance (NMR) spinning sideband patterns is considered. In disordered or amorphous materials a distribution in the magnitude of the (1)H-(1)H dipolar coupling is a realistic possibility. Simulations of the (1)H DQ MAS NMR spinning sideband spectra were performed with the two-spin approximation. These simulations reveal that a dipolar coupling distribution can greatly affect the DQ spectral shape and behavior of the DQ build-up. The spectral line shapes are quantified by measurement of the relative intensities of the DQ sidebands. These variations in the (1)H DQ NMR spectra are evaluated as a function of the width of the dipolar coupling distribution. As an example, the experimental DQ spinning sideband spectrum for a hydrated polyoxoniobate containing 15 H(2)O molecules per hexaniobate cluster, are better simulated with a distribution of dipolar couplings opposed to a single coupling constant.
Two-dimensional (2D) cross-polarization magic angle spinning (CP-MAS) (2)H-(13)C heteronuclear correlation (HETCOR) experiments were utilized to indirectly detect site-specific deuterium MAS powder patterns. The (2)H-(13)C... more
Two-dimensional (2D) cross-polarization magic angle spinning (CP-MAS) (2)H-(13)C heteronuclear correlation (HETCOR) experiments were utilized to indirectly detect site-specific deuterium MAS powder patterns. The (2)H-(13)C cross-polarization efficiency is orientation-dependent and non-uniform for all crystallites. This leads to difficulty in extracting the correct (2)H MAS quadrupole powder patterns. In order to obtain accurate deuterium line shapes, (13)C spin lock rf field, spin lock rf ramp and CP contact time were carefully calibrated with the assistance of theoretical simulations. The extracted quadrupole patterns for U-[(2)H/(13)C/(15)N]-alanine indicate that the methyl deuterium undergoes classic, three-site jumping in the fast motion regime (10(-8)-10(-12)s) and the methine deuterium has a rigid deuterium powder pattern. For U-[(2)H/(13)C/(15)N]-phenylalanine, indirectly detected deuterium line shapes illustrate that the aromatic ring undergoes 180° flips in the fast motion regime while (2)Hβ and (2)Hα are completely rigid. The experimental deuterium line shapes for U-[(2)H/(13)C/(15)N]-proline reflect that (2)Hβ, (2)Hγ and (2)Hδ are subjected to fast, two-site reorientations at an angle of (15±5)°, (30±5)° and (25±10)° respectively. In addition, an approach that combines a composite inversion pulse with (2)H-(13)C CP-MAS is applied to measure (2)H spin-lattice relaxation times in a site-specific, (13)C-detected fashion.
... Specifically, both static and magic angle spinning (MAS) NMR spectra are presented for and containing various amounts of ion-exchanged and ... F. Leroux, BE Koene, and LF Nazar, “Electrochemical Lithium Intercalation into a... more
... Specifically, both static and magic angle spinning (MAS) NMR spectra are presented for and containing various amounts of ion-exchanged and ... F. Leroux, BE Koene, and LF Nazar, “Electrochemical Lithium Intercalation into a Polyaniline/V[sub 2]O[sub 5] Nanocomposite,” J ...

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