Matching Items (10)
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- All Subjects: Physical Chemistry
- Creators: Richert, Ranko
- Creators: Yarger, Jeffery L
- Member of: ASU Electronic Theses and Dissertations
Description
The objective of the present investigations is to experimentally determine the fundamental molecular properties of the transient metal containing pieces. The transient molecules have been generated using laser ablation production technique and detected by using laser induced fluorescence technique. Ultra-high resolution spectra of the diatomic molecules, 87SrF, 135&137BaF, YbF, HfF, and IrSi were recorded at a resolution of approximately 30 Mhz. The fine and hyperfine structure of these molecules were determined for the ground and the excited state. The optical Stark splittings of 180HfF and IrSi were recorded and analyzed to determine the permanent electric dipole moments of the ground and the excited state. An effective Hamiltonian operator, including the rotational, centrifugal distortion, spin-orbit, spin-spin, spin-rotation, Λ-doubling, magnetic hyperfine and quadrupole interactions, and Stark effect, was employed to model and analyze the recorded spectra. The electronic spectra of the triatomic molecules, TiO2 and ZrO2, were recorded using pulsed dye laser, LIF, spectrometer at a resolution of 300MHz. These molecules have C2v symmetry. The harmonic frequencies, lifetime measurements were determined. These spectra of ZrO2 and TiO2 were modeled using a normal coordinate analysis and Franck-Condon factor predictions. High resolution field-free and Stark effect spectra of ZrO2 were recorded and for future investigation.
ContributorsLe, Anh Thun (Author) / Steimle, Timothy C (Thesis advisor) / Richert, Ranko (Committee member) / Chizmeshya, Andrew (Committee member) / Arizona State University (Publisher)
Created2013
Description
Molecular structures and dynamics in amorphous materials present unique experimental challenges compared with the characterization of crystalline solids. Liquids and glassy solids have many applications in industry such as ionic liquids for fuel cells or biomolecule stabilizing agents, enhancing pharmaceuticals dissolution rates, and modified high performance biopolymers like silk for textile, biomedical, drug delivery, among many others. Amorphous materials are metastable, with kinetic profiles of phase transitions depending on relaxation dynamics, thermal history, plus factors such as temperature, pressure, and humidity. Understanding molecular structure and phase transitions of amorphous states of small molecules and biopolymers is broadly important for realizing their applications. The structure of liquid and glassy states of the drugs carbamazepine (CBZ) and indomethacin (IMC) were studied with solid-state nuclear magnetic resonance (ssNMR) spectroscopy, high energy X-ray diffraction, Fourier Infrared Transform Spectroscopy (FTIR), differential scanning calorimetry (DSC), and Empirical Potential Structure Refinement (EPSR). Both drugs have multiple crystalline polymorphs with slow dissolution kinetics, necessitating stable glassy or polymer dispersed formulations. More hydrogen bonds per CBZ molecule and a larger distribution of oligomeric states in the glass versus the liquid than expected. The chlorobenzyl ring of crystalline and glassy IMC measured with ssNMR were surprisingly found to have similar mobility. Crucially, humidity strongly affects glass structure, highlighting the importance of combining modeling techniques like EPSR with careful sample preparation for proper interpretation. Highly basic protic ionic liquids with low ∆pKa were synthesized with metathesis rather than proton transfer and characterized using NMR and dielectric spectroscopy. Finally, the protein secondary structure of spider egg sac silk was studied using ssNMR, FTIR, and scanning electron microscopy. Tubuliform silk found in spider egg sacs has extensive β-sheet domains which form nanocrystallites within an amorphous matrix. Structural predictions and spectroscopic measurements of tubuliform silk solution are mostly α-helical, with the mechanism of structural rearrangement to the β-sheet rich fiber unknown. The movement of spiders during egg silk spinning make in situ experiments difficult practically. This work is the first observation that tubuliform silk of Argiope aurantia after liquid crystalline spinning exits the spinneret as a predominantly (~70%) β-sheet fiber.
ContributorsEdwards, Angela Diane (Author) / Yarger, Jeffery L (Thesis advisor) / Liu, Yan (Committee member) / Mujica, Vladimiro (Committee member) / Arizona State University (Publisher)
Created2022
Description
As the simplest carboxylic acid, formic acid (FA) is ubiquitous to Earth’s atmosphere, helping seed cloud nucleation and leading to acid rain. By studying the interactions between FA and high intensity light under high vacuum, conditions similar to the upper atmosphere, on other planets (either in the solar system or beyond), and even in interstellar media are emulated. These results were produced from a home built vacuum chamber system, with a Wiley-McLaren time of flight mass spectrometer and using femtosecond (fs) laser pulses. The laser characteristics were as follows: a pulse width >35 fs, center wavelength of 400 nm (probe pulse was 800 nm for the pump-probe investigation), and laser intensities at ~1015 W/cm2.At high laser intensities, the first direct experimental evidence of CO3+ was recorded from the Coulomb explosion (CE) of the formic acid dimer (FAD) from a molecular beam. Theoretical calculations provided further evidence for the formation of CO3+ from the vertical ionization of FAD. When (FA)n(H2O)mH+ clusters (n = 1-7 and m = 0-1) were exposed to similar laser intensities, the larger clusters (n = 5-7) favored complete atomization from CE, indicating that the repulsive forces within the clusters at those sizes was too great to withstand to form CO3+. The protonated nature of the clusters and the peak shapes recorded in the mass spectra suggested that neutral (FA)n+ clusters undergo a dissociation mechanism within the extraction region. A novel technique was created to calculate these dissociation times on the order of 100s of nanoseconds (ns), increasing by ~10 ns for each additional FA molecule. Using pump-probe spectroscopy, it was observed similarly that neutral (FA)n clusters with n > 1, showed evidence of ion pair formation of the form [(FA)nH+·OOCH-] on the sub-picosecond timescale, increasing by 70 fs per FA molecule. Both trends indicate that the neutral clusters prefer to form compact 3d structures, but after photoexcitation the clusters have competing pathways to ionization, either through multiphoton ionization (ns dynamics) or ion pair formation (fs dynamics) that inevitably lead to the expansion and subsequent rearrangement into linear chains for the protonated cluster.
ContributorsSutton, Shaun (Author) / Sayres, Scott G. (Thesis advisor) / Richert, Ranko (Committee member) / Chizmeshya, Andrew (Committee member) / Arizona State University (Publisher)
Created2023
Description
A driving force for studies of water, alcohols, and amides is the determination of the role of hydrogen bonding. Hydrogen bonds can break and reform, consequently creating supramolecular structures. Understanding the role supramolecular structures play in the dynamics of monohydroxyl alcohols is important to understanding hydrogen bonding in more complex systems such as proteins. Since many monohydroxyl alcohols are good glass formers, dielectric spectroscopy in the supercooled regime is used to gather information about the dynamics of these liquids. Application of high external fields will reversibly alter the polarization responses of the material from the linear response. This results in nonlinear dielectric effects (NDE) such as field induced suppression (saturation) and enhancement of amplitudes (chemical effects) as well as shifts in the time constants toward slower (entropy) and faster (energy absorption) dynamics.
The first part of this thesis describes the nonlinear dielectric experiments on monohydroxyl alcohols, with an emphasis on the time dependence of NDEs. For the first time, time-dependent experiments on monoalcohols were done, the results showed that NDEs occur on the Debye time scale. Furthermore, physical vapor deposition (PVD) is used to modify the supramolecular structure of 4-methyl-3-heptanol. Upon deposition the film cannot form the ring like structures, which are preferred in the bulk material. The as deposited film shows an enhancement of the dielectric peak by a factor of approximately 11 when compared to the bulk material. The conversion from the as deposited material back to the near bulk material was found to occur on the Debye timescale.
The second part of this thesis focuses on the question of what is governing the field induced changes seen in the liquids studied. Here a complete set of high field experiments on highly polar propylene carbonate derivatives were performed. It was demonstrated that these materials exhibit a Debye-like peak and using a combination of Adam-Gibbs and Fröhlich’s definition of entropy, proposed by Johari [G.P. Johari, J. Chem. Phys 138, 154503 (2013)], cannot solely be used to describe a frustration of dynamics. It is important to note that although these material exhibit a Debye like peak, the behavior is much different than monoalcohols.
The first part of this thesis describes the nonlinear dielectric experiments on monohydroxyl alcohols, with an emphasis on the time dependence of NDEs. For the first time, time-dependent experiments on monoalcohols were done, the results showed that NDEs occur on the Debye time scale. Furthermore, physical vapor deposition (PVD) is used to modify the supramolecular structure of 4-methyl-3-heptanol. Upon deposition the film cannot form the ring like structures, which are preferred in the bulk material. The as deposited film shows an enhancement of the dielectric peak by a factor of approximately 11 when compared to the bulk material. The conversion from the as deposited material back to the near bulk material was found to occur on the Debye timescale.
The second part of this thesis focuses on the question of what is governing the field induced changes seen in the liquids studied. Here a complete set of high field experiments on highly polar propylene carbonate derivatives were performed. It was demonstrated that these materials exhibit a Debye-like peak and using a combination of Adam-Gibbs and Fröhlich’s definition of entropy, proposed by Johari [G.P. Johari, J. Chem. Phys 138, 154503 (2013)], cannot solely be used to describe a frustration of dynamics. It is important to note that although these material exhibit a Debye like peak, the behavior is much different than monoalcohols.
ContributorsYoung-Gonzales, Amanda R (Author) / Richert, Ranko (Thesis advisor) / Angell, Charles (Committee member) / Wolf, George (Committee member) / Arizona State University (Publisher)
Created2019
Description
Transient molecules are of great importance having proposed applications in quantum science and technology and tests of fundamental physics. In the present dissertation, the transient molecules studied are SrOH, ThF, ThCl, YbF and YbOH; each having been selected because of their proposed application. Specifically, SrOH is a candidate of constructing a molecular magneto-optical trap (MOT). The simple actinide molecules, ThF and ThCl, were selected as ligand bonding model systems to gain insight into chemical processing of Spent Nuclear Fuel. The lanthanides YbF and YbOH are venues for the determination of electron electric dipole moment (eEDM) and the studies in this dissertation provide the requisite properties for those experiments.
Intense supersonic molecular beams of these transient molecules were generated via laser ablation and spectroscopically characterized using a novel medium-resolution two-dimensional (2D) spectroscopic approach, as well as high-resolution laser induced fluorescence (LIF). The 2D medium resolution approach, which was used in the studies SrOH, ThF, ThCl and YbOH, uses a multiplexing method that simultaneously records dispersed fluorescence and excitation spectra. A significant advantage of 2D-LIF imaging is that all the electronics states can be targeted to determine the electronics states and associated vibrational spacing individually. Consequently, in the 2D spectra of ThF, ThCl and YbOH, several previously unobserved band systems have been detected in one single scan. For the DF spectra of SrOH and YbOH, the determined branching ratios show that the transitions of these molecules are diagonal (i.e. Δv=0), which is essential for the proposed potential for laser cooling. In the high-resolution of YbF, ThF, ThCl and SrOH optical spectra were recorded to an accuracy of ±30 MHz, which represents an unprecedented precision of 1:10+8.
In addition to field free spectra, optical Stark and Zeeman studies were performed to determine the most fundamental magneto-and electro-static properties. Effective Hamiltonian operators were employed to analyze the recorded spectra and determine the spectroscopic parameters. This data set also establishes a contribution toward developing new computational methodologies for treating relativistic effects and electron correlation.
Intense supersonic molecular beams of these transient molecules were generated via laser ablation and spectroscopically characterized using a novel medium-resolution two-dimensional (2D) spectroscopic approach, as well as high-resolution laser induced fluorescence (LIF). The 2D medium resolution approach, which was used in the studies SrOH, ThF, ThCl and YbOH, uses a multiplexing method that simultaneously records dispersed fluorescence and excitation spectra. A significant advantage of 2D-LIF imaging is that all the electronics states can be targeted to determine the electronics states and associated vibrational spacing individually. Consequently, in the 2D spectra of ThF, ThCl and YbOH, several previously unobserved band systems have been detected in one single scan. For the DF spectra of SrOH and YbOH, the determined branching ratios show that the transitions of these molecules are diagonal (i.e. Δv=0), which is essential for the proposed potential for laser cooling. In the high-resolution of YbF, ThF, ThCl and SrOH optical spectra were recorded to an accuracy of ±30 MHz, which represents an unprecedented precision of 1:10+8.
In addition to field free spectra, optical Stark and Zeeman studies were performed to determine the most fundamental magneto-and electro-static properties. Effective Hamiltonian operators were employed to analyze the recorded spectra and determine the spectroscopic parameters. This data set also establishes a contribution toward developing new computational methodologies for treating relativistic effects and electron correlation.
ContributorsNguyen, Duc Trung (Author) / Steimle, Timothy C (Thesis advisor) / Richert, Ranko (Committee member) / Chizmeshya, Andrew V.G. (Committee member) / Arizona State University (Publisher)
Created2019
Description
How water behaves at interfaces is relevant to many scientific and technological applications; however, many subtle phenomena are unknown in aqueous solutions. In this work, interfacial structural transition in hydration shells of a polarizable solute at critical polarizabilities is discovered. The transition is manifested in maximum water response, the reorientation of the water dipoles at the interface, and an increase in the density of dangling OH bonds. This work also addresses the role of polarizability of the active site of proteins in biological catalytic reactions. For proteins, the hydration shell becomes very heterogeneous and involves a relatively large number of water molecules. The molecular dynamics simulations show that the polarizability, along with the atomic charge distribution, needs to be a part of the picture describing how enzymes work. Non Gaussian dynamics in time-resolved linear and nonlinear (correlation) 2D spectra are also analyzed.
Additionally, a theoretical formalism is presented to show that when preferential orientations of water dipoles exist at the interface, electrophoretic charges can be produced without free charge carriers, i.e., neutral solutes can move in a constant electric field due to the divergence of polarization at the interface. Furthermore, the concept of interface susceptibility is introduced. It involves the fluctuations of the surface charge density caused by thermal motion and its correlation over the characteristic correlation length with the fluctuations of the solvent charge density. Solvation free energy and interface dielectric constant are formulated accordingly. Unlike previous approaches, the solvation free energy scales quite well in a broad range of ion sizes, namely in the range of 2-14 A° . Interface dielectric constant is defined such that the boundary conditions in the Laplace equation describing a micro- or mesoscopic interface are satisfied. The effective dielectric constant of interfacial water is found to be significantly lower than its bulk value. Molecular dynamics simulation results show that the interface dielectric constant for a TIP3P water model changes from nine to four when the effective solute radius is increased from 5 A° to 18 A° . The small value of the interface dielectric constant of water has potentially dramatic consequences for hydration.
Additionally, a theoretical formalism is presented to show that when preferential orientations of water dipoles exist at the interface, electrophoretic charges can be produced without free charge carriers, i.e., neutral solutes can move in a constant electric field due to the divergence of polarization at the interface. Furthermore, the concept of interface susceptibility is introduced. It involves the fluctuations of the surface charge density caused by thermal motion and its correlation over the characteristic correlation length with the fluctuations of the solvent charge density. Solvation free energy and interface dielectric constant are formulated accordingly. Unlike previous approaches, the solvation free energy scales quite well in a broad range of ion sizes, namely in the range of 2-14 A° . Interface dielectric constant is defined such that the boundary conditions in the Laplace equation describing a micro- or mesoscopic interface are satisfied. The effective dielectric constant of interfacial water is found to be significantly lower than its bulk value. Molecular dynamics simulation results show that the interface dielectric constant for a TIP3P water model changes from nine to four when the effective solute radius is increased from 5 A° to 18 A° . The small value of the interface dielectric constant of water has potentially dramatic consequences for hydration.
ContributorsDinpajooh, Mohammadhasan (Author) / Matyushov, Dmitry V (Thesis advisor) / Richert, Ranko (Committee member) / Beckstein, Oliver (Committee member) / Arizona State University (Publisher)
Created2016
Description
Plastic crystals as a class are of much interest in applications as solid state electrolytes for electrochemical energy conversion devices. A subclass exhibit very high protonic conductivity and its members have been investigated as possible fuel cell electrolytes, as first demonstrated by Haile’s group in 2001 with CsHSO4. To date these have been inorganic compounds with tetrahedral oxyanions carrying one or more protons, charge-balanced by large alkali cations. Above the rotator phase transition, the HXO4- anions re-orient at a rate dependent on temperature while the centers of mass remain ordered. The transition is accompanied by a conductivity "jump" (as much as four orders of magnitude, to ~ 10 mScm-1 in the now-classic case of CsHSO4) due to mobile protons. These superprotonic plastic crystals bring a “true solid state” alternative to polymer electrolytes, operating at mild temperatures (150-200ºC) without the requirement of humidification. This work describes a new class of solid acids based on silicon, which are of general interest. Its members have extraordinary conductivities, as high as 21.5 mS/cm at room temperature, orders of magnitude above any previous reported case. Three fuel cells are demonstrated, delivering current densities as high as 225 mA/cm2 at short-circuit at 130ºC in one example and 640 mA/cm2 at 87ºC in another. The new compounds are insoluble in water, and their remarkably high conductivities over a wide temperature range allow for lower temperature operations, thus reducing the risk of hydrogen sulfide formation and dehydration reactions. Additionally, plastic crystals have highly advantageous properties that permit their application as solid state electrolytes in lithium batteries. So far only doped materials have been presented. This work presents for the first time non-doped plastic crystals in which the lithium ions are integral part of the structure, as a solid state electrolyte. The new electrolytes have conductivities of 3 to 10 mS/cm at room temperature, and in one example maintain a highly conductive state at temperatures as low as -30oC. The malleability of the materials and single ion conducting properties make these materials highly interesting candidates as a novel class of solid state lithium conductors.
ContributorsKlein, Iolanda Santana (Author) / Angell, Charles A (Thesis advisor) / Buttry, Daniel A (Committee member) / Richert, Ranko (Committee member) / Arizona State University (Publisher)
Created2016
Description
Spider dragline silk is well known for its outstanding mechanical properties - a combination of strength and extensibility that makes it one of the toughest materials known. Two proteins, major ampullate spidroin 1 (MaSp1) and 2 (MaSp2), comprise dragline silk fibers. There has been considerable focus placed on understanding the source of spider silk's unique mechanical properties by investigating the protein composition, molecular structure and dynamics. Chemical compositional heterogeneity of spider silk fiber is critical to understand as it provides important information for the interactions between MaSp1 and MaSp2. Here, the amino acid composition of dragline silk protein was precisely determined using a solution-state nuclear magnetic resonance (NMR) approach on hydrolyzed silk fibers. In a similar fashion, solution-state NMR was applied to probe the "13"C/"15"N incorporation in silk, which is essential to understand for designing particular solid-state NMR methods for silk structural characterization. Solid-state NMR was used to elucidate silk protein molecular dynamics and the supercontraction mechanism. A "2"H-"13"C heteronuclear correlation (HETCOR) solid-state NMR technique was developed to extract site-specific "2"H quadrupole patterns and spin-lattice relaxation rates for understanding backbone and side-chain dynamics. Using this technique, molecular dynamics were determined for a number of repetitive motifs in silk proteins - Ala residing nanocrystalline &beta-sheet; domains, 3"1"-helical regions, and, Gly-Pro-Gly-XX &beta-turn; motifs. The protein backbone and side-chain dynamics of silk fibers in both dry and wet states reveal the impact of water on motifs with different secondary structures. Spider venom is comprised of a diverse range of molecules including salts, small organics, acylpolyamines, peptides and proteins. Neurotoxins are an important family of peptides in spider venom and have been shown to target and modulate various ion channels. The neurotoxins are Cys-rich and share an inhibitor Cys knot (ICK) fold. Here, the molecular structure of one G. rosea tarantula neurotoxin, GsAF2, was determined by solution-state NMR. In addition, the interaction between neurotoxins and model lipid bilayers was probed with solid-state NMR and negative-staining (NS) transmission electron microscopy (TEM). It is shown that the neurotoxins influence lipid bilayer assembly and morphology with the formation of nanodiscs, worm-like micelles and small vesicles.
ContributorsShi, Xiangyan (Author) / Yarger, Jeffery L (Thesis advisor) / Holland, Gregory P (Thesis advisor) / Levitus, Marcia (Committee member) / Marzke, Robert F (Committee member) / Arizona State University (Publisher)
Created2014
Description
The bonding and electrostatic properties of gold containing molecules are highly influenced by relativistic effects. To understand this facet on bonding, a series of simple diatomic AuX (X=F, Cl, O and S) molecules, where upon bond formation the Au atom donates or accepts electrons, was investigated and discussed in this thesis.
First, the optical field-free, Stark, and Zeeman spectroscopic studies have been performed on AuF and AuCl. The simple polar bonds between Au and typical halogens (i.e. F and Cl) can be well characterized by the electronic structure studies and the permanent electric dipole moments, el. The spectroscopic parameters have been precisely determined for the [17.7]1, [17.8]0+ and X1+ states of AuF, and the [17.07]1, [17.20]0+ and X1+ states of AuCl. The el have been determined for ground and excited states of AuF and AuCl. The results from the hyperfine analysis and Stark measurement support the assignments that the [17.7]1 and [17.8]0+ states of AuF are the components of a 3 state. Similarly, the analysis demonstrated the [19.07]1 and [19.20]0+ states are the components of the 3 state of AuCl.
Second, my study focused on AuO and AuS because the bonding between gold and sulfur/oxygen is a key component to numerous established and emerging technologies that have applications as far ranging as medical imaging, catalysis, electronics, and material science. The high-resolution spectra were record and analyzed to obtain the geometric and electronic structural data for the ground and excited states. The electric dipole moment, el, and the magnetic dipole moment, m, has been the precisely measured by applying external static electric and magnetic fields. el andm are used to give insight into the unusual complex bonding in these molecules.
In addition to direct studies on the gold-containing molecules, other studies of related molecules are included here as well. These works contain the pure rotation measurement of PtC, the hyperfine and Stark spectroscopic studies of PtF, and the Stark and Zeeman spectroscopic studies of MgH and MgD.
Finally, a perspective discussion and conclusion will summarize the results of AuF, AuCl, AuO, and AuS from this work (bond lengths, dipole moment, etc.). The highly quantitative information derived from this work is the foundation of a chemical description of matter and essential for kinetic energy manipulation via Stark and Zeeman interactions. This data set also establishes a synergism with computation chemists who are developing new methodologies for treating relativistic effects and electron correlation.
First, the optical field-free, Stark, and Zeeman spectroscopic studies have been performed on AuF and AuCl. The simple polar bonds between Au and typical halogens (i.e. F and Cl) can be well characterized by the electronic structure studies and the permanent electric dipole moments, el. The spectroscopic parameters have been precisely determined for the [17.7]1, [17.8]0+ and X1+ states of AuF, and the [17.07]1, [17.20]0+ and X1+ states of AuCl. The el have been determined for ground and excited states of AuF and AuCl. The results from the hyperfine analysis and Stark measurement support the assignments that the [17.7]1 and [17.8]0+ states of AuF are the components of a 3 state. Similarly, the analysis demonstrated the [19.07]1 and [19.20]0+ states are the components of the 3 state of AuCl.
Second, my study focused on AuO and AuS because the bonding between gold and sulfur/oxygen is a key component to numerous established and emerging technologies that have applications as far ranging as medical imaging, catalysis, electronics, and material science. The high-resolution spectra were record and analyzed to obtain the geometric and electronic structural data for the ground and excited states. The electric dipole moment, el, and the magnetic dipole moment, m, has been the precisely measured by applying external static electric and magnetic fields. el andm are used to give insight into the unusual complex bonding in these molecules.
In addition to direct studies on the gold-containing molecules, other studies of related molecules are included here as well. These works contain the pure rotation measurement of PtC, the hyperfine and Stark spectroscopic studies of PtF, and the Stark and Zeeman spectroscopic studies of MgH and MgD.
Finally, a perspective discussion and conclusion will summarize the results of AuF, AuCl, AuO, and AuS from this work (bond lengths, dipole moment, etc.). The highly quantitative information derived from this work is the foundation of a chemical description of matter and essential for kinetic energy manipulation via Stark and Zeeman interactions. This data set also establishes a synergism with computation chemists who are developing new methodologies for treating relativistic effects and electron correlation.
ContributorsZhang, Ruohan (Author) / Steimle, Timothy C. (Thesis advisor) / Williams, Peter (Committee member) / Richert, Ranko (Committee member) / Arizona State University (Publisher)
Created2017
Description
Nanomaterials have attracted considerable attention in recent research due to their wide applications in various fields such as material science, physical science, electrical engineering, and biomedical engineering. Researchers have developed many methods for synthesizing different types of nanostructures and have further applied them in various applications. However, in many cases, a molecular level understanding of nanoparticles and their associated surface chemistry is lacking investigation. Understanding the surface chemistry of nanomaterials is of great significance for obtaining a better understanding of the properties and functions of the nanomaterials. Nuclear magnetic resonance (NMR) spectroscopy can provide a familiar means of looking at the molecular structure of molecules bound to surfaces of nanomaterials as well as a method to determine the size of nanoparticles in solution. Here, a combination of NMR spectroscopic techniques including one- and two-dimensional NMR spectroscopies was used to investigate the surface chemistry and physical properties of some common nanomaterials, including for example, thiol-protected gold nanostructures and biomolecule-capped silica nanoparticles.
Silk is a natural protein fiber that features unique properties such as excellent mechanical properties, biocompatibility, and non-linear optical properties. These appealing physical properties originate from the silk structure, and therefore, the structural analysis of silk is of great importance for revealing the mystery of these impressive properties and developing novel silk-based biomaterials as well. Here, solid-state NMR spectroscopy was used to elucidate the secondary structure of silk proteins in N. clavipes spider dragline silk and B. mori silkworm silk. It is found that the Gly-Gly-X (X=Leu, Tyr, Gln) motif in spider dragline silk is not in a β-sheet or α-helix structure and is very likely to be present in a disordered structure with evidence for 31-helix confirmation. In addition, the conformations of the Ala, Ser, and Tyr residues in silk fibroin of B. mori were investigated and it indicates that the Ala, Ser, and Tyr residues are all present in disordered structures in silk I (before spinning), while show different conformations in silk II (after spinning). Specifically, in silk II, the Ala and Tyr residues are present in both disordered structures and β-sheet structures, and the Ser residues are present primarily in β-sheet structures.
Silk is a natural protein fiber that features unique properties such as excellent mechanical properties, biocompatibility, and non-linear optical properties. These appealing physical properties originate from the silk structure, and therefore, the structural analysis of silk is of great importance for revealing the mystery of these impressive properties and developing novel silk-based biomaterials as well. Here, solid-state NMR spectroscopy was used to elucidate the secondary structure of silk proteins in N. clavipes spider dragline silk and B. mori silkworm silk. It is found that the Gly-Gly-X (X=Leu, Tyr, Gln) motif in spider dragline silk is not in a β-sheet or α-helix structure and is very likely to be present in a disordered structure with evidence for 31-helix confirmation. In addition, the conformations of the Ala, Ser, and Tyr residues in silk fibroin of B. mori were investigated and it indicates that the Ala, Ser, and Tyr residues are all present in disordered structures in silk I (before spinning), while show different conformations in silk II (after spinning). Specifically, in silk II, the Ala and Tyr residues are present in both disordered structures and β-sheet structures, and the Ser residues are present primarily in β-sheet structures.
ContributorsGuo, Chengchen (Author) / Yarger, Jeffery L (Thesis advisor) / Holland, Gregory P (Thesis advisor) / Buttry, Daniel A (Committee member) / Wang, Xu (Committee member) / Arizona State University (Publisher)
Created2017