Helix Dipole Research Articles

Stimuli-Responsive Oligourea Molecular Films.

We have designed and synthesized a helical cysteamine-terminated oligourea foldamer composed of ten urea residues featuring side carboxyl and amine groups. The carboxyl group is located in proximity to the C-terminus of the oligourea and hence at the negative pole of the helix dipole. The amine group is located close to the N-terminus and hence at the positive pole of the helix dipole. Beyond the already remarkable dipole moment inherent in oligourea 2.5 helices, the incorporation of additional charges originating from the carboxylic and amine groups is supposed to impact the overall charge distribution along the molecule. These molecules were self-assembled into monolayers on a gold substrate, allowing us to investigate the influence of an electric field on these polar helices. By applying surface-enhanced infrared reflection-absorption spectroscopy, we proved that molecules within the monolayers tend to reorient themselves more vertically when a negative bias is applied to the surface. It was also found that surface-confined oligourea molecules affected by the external electric field tend to rearrange the electron density at urea groups, leading to the stabilization of the resonance structure with charge transfer character. The presence of the external electric field also affected the nanomechanical properties of the oligourea films, suggesting that molecules also tend to reorient in the ambient environment without an electrolyte solution. Under the same conditions, the helical oligourea displayed a robust piezoresponse, particularly noteworthy given the slender thickness of the monolayer, which measured approximately 1.2 nm. This observation demonstrates that thin molecular films composed of oligoureas may exhibit stimulus-responsive properties. This, in turn, may be used in nanotechnology systems as actuators or functional films, enabling precise control of their thickness in the range of even fractions of nanometers.

Exploring voltage sensing in protein-translocating channel SecYEG.

The conserved protein translocation channel SecYEG facilitates protein transport across as well as integration into the membrane. To maintain ion gradients across the membrane, essential for many cellular processes, it is of utmost importance that the Sec channel remains impermeable to these ions despite its bulky substrates. It has been shown via electrophysiological experiments that physiological levels of transmembrane voltage allow the channel to stay impermeable. Yet, the substrate-bound SecYEG becomes leaky once the absolute value of the transmembrane voltage drops below a certain threshold [1,2]. We proposed that the dipole moment of helix 2b is responsible for voltage sensing and that other complex parts must also contribute [3]. Molecular dynamics simulations suggested the involvement of the 5th helix dipole. Replacing S188 on its cytoplasmatic terminus allowed reverting its electrostatic contribution. Here, we measured the kinetics of voltage-gated closings of the thus mutated bacterial SecYEG translocon, reconstituted into planar bilayers. The translocon openings were triggered by the binding of ribosome nascent chain complexes harboring the voltage sensor domain of the voltage-gated potassium channel KvAP. S188E exhibited an increased voltage sensitivity, whereas S188R partially de-sensitized the translocon. Our results confirm the earlier hypothesis, in which the dipole moment of multiple TM-helices serves as SecYEG's voltage sensor. Support of the Austrian Science Fund (FWF), grant P34584 to PP, is gratefully acknowledged.

In silico assessment of missense point mutations on human cathelicidin LL-37

Cathelicidin antimicrobial peptides are a diverse family of cationic amphipathic peptides with multiple activities. In humans, cathelicidin LL-37 is one of the main host defense peptides with a remarkable medical and biotechnological potential. Deregulation of LL-37 expression has been associated with inflammatory diseases. However the effects of point mutations driven by single nucleotide polymorphisms (SNPs) on LL-37 are unknown. Here we applied an array of computational tools to investigate the effects of such mutations on LL-37 structure and activity. Due to the fact that, on cathelicidins, the prodomain is more conserved than the mature peptide, the SNP effect predictions were biased and, overall, resulted in neutral effects; and due to the slight changes in physicochemical properties, the antimicrobial predictions indicated the maintenance of such activity. Nonetheless, R07P, R07W, R29Q, R29W mutations reduced the peptide net charge, which in turn could result in less active LL-37 variants. Molecular dynamics data indicated that R07Q and N30Y mutations altered the LL-37 structure, leading to potential deleterious effects. In addition, the helix dipole is altered in G03A, R07P, R07W and L31P mutations, which could also alter the antimicrobial activity. Our results indicated that despite the mutations did not alter the residues from LL-37 active core, they could influence the antimicrobial activity and consequently, could be involved in inflammatory diseases.

The influence of structure uniformity on resonant frequency of ultra-high frequency radio frequency identification tag thread With normal mode helix dipole antenna

The stable performance of ultra-high frequency radio frequency identification (UHF RFID) tag thread with normal mode helical dipole antenna (NMHDA) was required for industrialized application. The ununiform helical pitches and helical radiuses caused by the unstable tension in the preparation process and material properties of carrying yarn probably deteriorate the performance of UHF RFID tag thread with NMHDA, while previous work focused on the properties of UHF RFID tag thread with uniform structure by finite element simulation. This work conducted numerical experiments with the actual statistical distribution of helical pitch and helical radius, i.e. normal distribution, and discussed the influence of the distributed parameters on resonant frequency. And then, the relationship between structure uniformity and resonant frequency was explored. Furthermore, the relationship was put into practice of the design of UHF RFID tag thread with stable properties. The results show that the fluctuation of resonant frequency first decreases and then increases with the increase of the mean helical pitch ( S me), and the resonant frequency decreases with the increase of the standard deviation of helical pitch ( S st) and that of helical radius ( r st). When the reactance of helical coil linearly changes with helical radius, the mean helical radius ( r me) has a negligible effect on the fluctuation of resonant frequency. The importance of the factors for the resonant frequency conforms to the following order: r me> S st> S me> r st. Additionally, the stable reading range of prototype (14.13 ± 0.06 m) demonstrated the practice of these results in the design of UHF RFID tag thread with NMHDA.

Physical relationship between resonant frequency and structure parameters of a normal mode helix dipole antenna for an ultra-high frequency radio frequency identification tag thread

The thread-based ultra-high frequency radio frequency identification (UHF RFID) tag with a normal mode helix dipole antenna (NMHDA) shows great potential in anti-theft and implant wireless sensors; for the engineered and digitized design of the high-performance tag, it is necessary to know the physical relationship between the resonant frequency and structure parameters of the NMHDA. Previous work for the design of the NMHDA structure is based on the self-resonant principle, that is, zero port reactance, while the port impedance of the NMHDA in the UHF RFID tag thread at resonant frequency is ideally conjugate matching to the chip. Under the requirement of conjugate matching, this study built the physical relationship between the resonant frequency and structural parameters of the NMHDA (helical radius, helical pitch, and single arm length) by linking the chip impedance with the NMHDA impedance. Meanwhile, the reported equivalent impedance model of the NMHDA, consisted of a lumped inductor and a linear dipole antenna, was utilized and modified by considering the distributed capacitance deviation from the NMHDA geometry simplification as part of the lumped inductor. Finally, the physical relationship was put into practice for the design of an UHF RFID tag thread with expected resonant frequency, and the long reading range of the prototype (over 14 m) demonstrated the rationality of the modification. In addition, the discussion on the structure parameter of the NMHDA clarified the efficiency of our proposed method. Generally, the built physical relationship explicitly gives the physical effects of the structural parameters and provides a parametric method for the structure design of a NMHDA for the UHF RFID tag thread.

The Multifaceted Subunit Interface of Malate Dehydrogenase

Most Malate Dehydrogenases are dimeric though there are a small number (for example the LDH like Apicomplexan Malate Dehydrogenases) with tetrameric structures. A variety of studies have shown the oligomeric structure to be important for the overall activity of the enzyme with roles from stability to allosteric interactions being suggested. To explore our overall hypothesis that regions of the subunit interface would be tailored to specific functions we initiated an examination of the cross interface interactions of malate dehydrogenases from a wide variety of organisms whose crystal structures are available. Using the Hawkdock MM/GBSA routine we determined the residues involved in the interface in each structure. For the dimer interface we found between 24 and 35 residues involved depending on isoform. Mapping these residues onto structures revealed 5 areas of interaction, I to V with regions II – V being spatially conserved in all structures (figure 1). Region I was found only in chloroplastic versions of MDH. While the general areas of contact are conserved the detailed nature of the interactions revealed significant differences including inclusion of a conserved repulsion in region II in all Isoforms. These observations led to a series of hypotheses concerning the roles of specific regions and residues in isoform families. We focused on the cross interface interactions potentially related to citrate regulation of the organelle isoforms, and identified a unique cross interface interaction between the sidechain of D87 and the helix dipole of helix T268‐286 on the opposite subunit adjacent to a D92‐Y273 interaction across the interface. The role of L269/S266 in this helix and adjacent loop which we hypothesized form a cross interface molecular switch, was explored using site directed mutagenesis which showed that mutation of either residue to alanine disrupted either oxaloacetate or NADH saturation, overall catalytic activity and citrate inhibition. These results suggest a cross interface network (figure 2) in organelle malate dehydrogenases. Comparison of interface residues from structures with and without Citrate bound show that region III and V show the largest changes induced by citrate with some residues showing greater and others lesser contributions to the interface and are consistent with the observed network of interactions and suggest that changes across the interface might be induced by citrate interacting with S266. Interestingly the tetrameric MDHs from Ignacoccus Islandicus and the apicomplexans shares many but not all of these residues, lacking in particular D92, T268 and Y273. Knock in mutants of the Ignacoccus Islandicus and the Plasmodium falciparum MDHs studied both computationally and with enzyme kinetics shed further insight on the potential roles of these residues and the evolution of cooperativity in MDH.

Testing Patch, Helix and Vertical Dipole GPS Antennas with without Choke Ring Frame

Abstract: The antenna is the connecting part between Global Positioning System (GPS) satellite and receiver, and it works on transferring the satellite signal propagation to the receiver with minimum interruption. This is beside the main role that GPS antenna can play for accurate and precise positioning. High quality GPS antennas have high gain, systematic radiation pattern, Right Hand Circular Polarization (RHCP), and low directivity. Multipath error is a principal error source connected with GPS positioning and it can be mitigated using better antenna design. GPS antennas tend to be provided with choke ring frame for protection from the reflected RHCP electromagnetic waves. In this paper, the performance of three different types of GPS antenna, namely: Microstrip Patch Antenna (MPA), Helix antenna (HA), and Vertical Dipole antenna (VDA), with and without choke ring frame, has been investigated using single frequency GPS receiver. The antennas have been examined under the same GPS environment, including satellites constellation, geometry, and surroundings, with different heights from the ground reflector surface for multipath evaluation. Short base-line kinematic differential code GPS (DGPS) technique has been used for removing and mitigating the main GPS error sources and focusing on multipath effect. Satellite residuals and the quality of the obtained positioning have been considered for evaluating the performance of each antenna. The results have reflected the ability of choke ring frames to improve the performance of the three GPS antennas with different rates in multipath areas, and illustrate the advantages and limitations of each antenna. Keywords: Micro-strip, Patch, Helix, Vertical Dipole, GPS, Choke Ring Antenna, Multipath.

Structure and function of an Arabidopsis thaliana sulfate transporter

Plant sulfate transporters (SULTR) mediate absorption and distribution of sulfate (SO42−) and are essential for plant growth; however, our understanding of their structures and functions remains inadequate. Here we present the structure of a SULTR from Arabidopsis thaliana, AtSULTR4;1, in complex with SO42− at an overall resolution of 2.8 Å. AtSULTR4;1 forms a homodimer and has a structural fold typical of the SLC26 family of anion transporters. The bound SO42− is coordinated by side-chain hydroxyls and backbone amides, and further stabilized electrostatically by the conserved Arg393 and two helix dipoles. Proton and SO42− are co-transported by AtSULTR4;1 and a proton gradient significantly enhances SO42− transport. Glu347, which is ~7 Å from the bound SO42−, is required for H+-driven transport. The cytosolic STAS domain interacts with transmembrane domains, and deletion of the STAS domain or mutations to the interface compromises dimer formation and reduces SO42− transport, suggesting a regulatory function of the STAS domain.

Structural and Mechanistic Insights into C-S Bond Formation in Gliotoxin.

Glutathione‐S‐transferases (GSTs) usually detoxify xenobiotics. The human pathogenic fungus Aspergillus fumigatus however uses the exceptional GST GliG to incorporate two sulfur atoms into its virulence factor gliotoxin. Because these sulfurs are essential for biological activity, glutathionylation is a key step of gliotoxin biosynthesis. Yet, the mechanism of carbon−sulfur linkage formation from a bis‐hydroxylated precursor is unresolved. Here, we report structures of GliG with glutathione (GSH) and its reaction product cyclo[‐l‐Phe‐l‐Ser]‐bis‐glutathione, which has been purified from a genetically modified A. fumigatus strain. The structures argue for stepwise processing of first the Phe and second the Ser moiety. Enzyme‐mediated dehydration of the substrate activates GSH and a helix dipole stabilizes the resulting anion via a water molecule for the nucleophilic attack. Activity assays with mutants validate the interactions of GliG with the ligands and enrich our knowledge about enzymatic C−S bond formation in gliotoxin and epipolythiodioxopiperazine (ETP) natural compounds in general.

Structure optimization of an ultrahigh frequency radio frequency identification tag thread based on the normal mode helix dipole antenna

This paper describes the design of a novel ultrahigh frequency radio frequency identification (UHF RFID) tag thread that mainly consisted of the common yarn and the normal mode helix dipole antenna. The linear dipole antenna for the UHF RFID tag thread was too long to miniaturize the tag. In order to maximize the read performance and miniaturize the size of the tag, the basic antenna structure parameters, such as the helical pitch and single arm length, were optimized by analyzing the radiation parameter S11 of the normal mode helix dipole antenna based on simulation experiments. The simulation experiments started with optimizing the single arm length to obtain the minimum of the S11 parameter at resonant frequency, then the helical pitch was further optimized to limit the resonant frequency to the UHF range. The simulation results showed the resonant frequency rises with an increase of helical pitch and declines with an increase of single arm length. Furthermore, a series of UHF RFID tag threads with good performance from the simulation cases were prepared, and the performance of the optimized tag was validated. Generally, the UHF RFID tag thread with optimized helix dipole antenna could reduce the axial length of the tag by 57% and improve the reading range by 500%, and its performance was greatly superior to that of the UHF RFID tag thread with the classical linear dipole antenna.

Helix Dipole and Membrane Electrostatics Delineate Conformational Transitions in the Self-Assembly of Amyloidogenic Peptides.

The self-assembly of amyloidogenic peptides on membrane surfaces is associated with the death of neurons and β-cells in Alzheimer's disease and type 2 diabetes, respectively. The early events of self-assembly in vivo are not known, but there is increasing evidence for the importance of the α-helix. To test the hypothesis that electrostatic interactions involving the helix dipole play a key role in membrane-mediated peptide self-assembly, we studied IAPP[11-25(S20G)-NH2] (R11LANFLVHSGNNFGA25-NH2), which under certain conditions self-assembles in hydro to form β-sheet assemblies through an α-helix-containing intermediate. In the presence of small unilamellar vesicles composed solely of zwitterionic lipids, the peptide does not self-assemble presumably because of the absence of stabilizing electrostatic interactions between the membrane surface and the helix dipole. In the presence of vesicles composed solely of anionic lipids, the peptide forms a long-lived α-helix presumably stabilized by dipole-dipole interactions between adjacent helix dipoles. This helix represents a kinetic trap that inhibits β-sheet formation. Intriguingly, when the amount of anionic lipids was decreased to mimic the ratio of zwitterionic and anionic lipids in cells, the α-helix was short-lived and underwent an α-helix to β-sheet conformational transition. Our work suggests that the helix dipole and membrane electrostatics delineate the conformational transitions occurring along the self-assembly pathway to the amyloid.

Electromagnetic analysis of wires with joints using a hybrid meshless-moments technique

This paper presents a fast and accurate hybrid method to analyze radiation of and scattering from conducting wire structures. The proposed technique is based on meshless method (MlM) and method of moments (MoM). First, the electric field integral equation (EFIE) is broken into two parts, integral and differential parts. In this paper, we use smooth meshless basis functions in evaluating the differential part and conventionally employ pulse basis functions in estimation of the integral part, given by closed-form expressions. We call this new technique, advanced meshless method (AMM) and use it to analyze wire structures such as helix and straight dipole antennas. Next, we investigate structures that include two wires connecting at a joint point, such as a helical dipole antenna that is composed of a quarter-wavelength dipole, connected to two helical wires at both its ends and also a folded dipole antenna that has two half-wavelength dipoles connected by two small half ring wires. We propose a new hybrid meshless-moments technique (MMT) which treats separate wire parts like the helical wire, half ring wire, and straight dipole parts by the AMM and the joint or connection parts by the MoM. The interactions between different parts are then taken into account by calculation of the near-field integral equations. Various comparisons between AMM and MMT results with those of a conventional MoM confirm that while accuracy is fixed the AMM and MMT are at least 10 times faster than MoM. The main feature of the hybrid MMT method is its computational efficiency in analyzing electrically large problems. As an example, extinction cross section of a chaff cloud composed of a large number of randomly placed and oriented helical particles as a function of frequency is efficiently computed by the hybrid MMT to show its capability in fast and accurate calculation of a complex medium dispersion.

Molecular Basis for Hormone Recognition and Activation of Corticotropin-Releasing Factor Receptors.

Corticotropin-releasing factor (CRF) and the three related peptides urocortins 1-3 (UCN1-UCN3) are endocrine hormones that control the stress responses by activating CRF1R and CRF2R, two members of class B G-protein-coupled receptors (GPCRs). Here, we present two cryoelectron microscopy (cryo-EM) structures of UCN1-bound CRF1R and CRF2R with the stimulatory G protein. In both structures, UCN1 adopts a single straight helix with its N terminus dipped into the receptor transmembrane bundle. Although the peptide-binding residues in CRF1R and CRF2R are different from other members of class B GPCRs, the residues involved in receptor activation and G protein coupling are conserved. In addition, both structures reveal bound cholesterol molecules to the receptor transmembrane helices. Our structures define the basis of ligand-binding specificity in the CRF receptor-hormone system, establish a common mechanism of class B GPCR activation and G protein coupling, and provide a paradigm for studying membrane protein-lipid interactions for class B GPCRs.

Structural preferences of cysteine sulfinic acid: The sulfinate engages in multiple local interactions with the peptide backbone

Cysteine sulfinic acid (Cys-SO2–) is a non-enzymatic oxidative post-translational modification (PTM) that has been identified in hundreds of proteins. However, the effects of cysteine sulfination are in most cases poorly understood. Cys-SO2– is structurally distinctive, with long sulfur-carbon and sulfur-oxygen bonds, and with tetrahedral geometry around sulfur due to its lone pair. Cys-SO2– thus has a unique range of potential interactions with the protein backbone which could facilitate protein structural changes. Herein, the structural effects of cysteine oxidation to the sulfinic acid were investigated in model peptides and folded proteins using NMR spectroscopy, circular dichroism, bioinformatics, and computational studies. In the PDB, Cys-SO2– shows a greater preference for α-helix than Cys. In addition, Cys-SO2– is more commonly found in structures with φ > 0, including in multiple types of β-turn. Sulfinate oxygens engage in hydrogen bonds with adjacent (i or i + 1) amide hydrogens. Over half of sulfinates have at least one hydrogen bond with an adjacent amide, and several structures have hydrogen bonds with both adjacent amides. Alternately, sulfur or either oxygen can act as an electron donor for n→π* interactions with the backbone carbonyl of the same residue, as indicated by frequent S⋯CO or O⋯CO distances below the sums of their van der Waals radii in protein structures. In peptides, Cys-SO2– favored α-helical structure at the N-terminus, consistent with helix dipole effects and backbone hydrogen bonds with the sulfinate promoting α-helix. Cys-SO2– has only modestly greater polyproline II helix propensity than Cys-SH, likely due to competition from multiple side chain-backbone interactions. Cys-SO2– stabilizes the i+1 position of a β-turn relative to Cys-SH. Within proteins, the range of side chain-main chain interactions available to Cys-SO2– compared to Cys-SH provides a basis for potential changes in protein structure and function due to cysteine oxidation to the sulfinic acid.

Electron Microscopic Detection of Single Membrane Proteins by a Specific Chemical Labeling.

SummaryElectron microscopy (EM) is a technology that enables visualization of single proteins at a nanometer resolution. However, current protein analysis by EM mainly relies on immunolabeling with gold-particle-conjugated antibodies, which is compromised by large size of antibody, precluding precise detection of protein location in biological samples. Here, we develop a specific chemical labeling method for EM detection of proteins at single-molecular level. Rational design of α-helical peptide tag and probe structure provided a complementary reaction pair that enabled specific cysteine conjugation of the tag. The developed chemical labeling with gold-nanoparticle-conjugated probe showed significantly higher labeling efficiency and detectability of high-density clusters of tag-fused G protein-coupled receptors in freeze-fracture replicas compared with immunogold labeling. Furthermore, in ultrathin sections, the spatial resolution of the chemical labeling was significantly higher than that of antibody-mediated labeling. These results demonstrate substantial advantages of the chemical labeling approach for single protein visualization by EM.

Intramolecular energies of the cytotoxic protein CagA of Helicobacter pylori as a possible descriptor of strains’ pathogenicity level

The Helicobacter pylori cytotoxin-associated gene A (CagA) is known for causing gastroduodenal diseases, such as atrophic gastritis and peptic ulcerations. Furthermore Helicobacter pylori CagA positive strains has been reported as one of the main risk factors for gastric cancer (Parsonnet et al., 1997). Structural variations in the CagA structure can alter its affinity with the host proteins, inducing differences in the pathogenicity of H. pylori. CagA N-terminal region is characterized for be conserved among all H. pylori strains since the C-terminal region is characterized by an intrinsically disorder behavior. We generated complete structural models of CagA using different conformations of the C-terminal region for two H. pylori strains. These models contain the same EPIYA (ABC1C2) motifs but different level of pathogenicity: gastric cancer and duodenal ulcer. Using these structural models we evaluated the pathogenicity level of the H. pylori strain, based on the affinity of the interaction with SHP-2 and Grb2 receptors and on the number of interactions with the EPIYA motif. We found that the main differences in the interaction was due to the contributions of certain types of energies from each strain and not from the total energy of the molecule. Specifically, the electrostatic energy, helix dipole energy, Wander Waals clashes, torsional clash, backbone clash and cis bond energy allowed a separation between severe and mild pathology for the interaction of only CagA with SHP2.

The GroEL chaperonin: a protein machine with pistons driven by ATP binding and hydrolysis.

In response to the binding of ATP, the two heptameric rings of the GroEL chaperonin protein interact with one another in a negatively cooperative manner. Owing to the helix dipole, the positively charged nitrogen of glycine 88 at the N-terminus of helix D binds to oxygen atoms on the β and γ phosphorus atoms of ATP. In apo-GroEL, the nucleotide-binding sites of different rings are connected to one another by the interaction of the ɛ-amino group of lysine 105 of one helix D across the twofold axis with the negatively charged carbonyl oxygen atom of alanine 109 at the C-terminus of the other helix D. Upon binding ATP, the K105–A109 salt bridge breaks and both helices move apart by approximately 3.5 Å en bloc toward the ATP. Upon hydrolysis of ATP, the helices return to their original position. The helices thus behave as pistons, their movement being driven by the binding and hydrolysis of ATP.This article is part of a discussion meeting issue ‘Allostery and molecular machines’.

Band 3 function and dysfunction in a structural context

Current research on the human band 3 glycoprotein, the red cell chloride/bicarbonate anion exchanger (AE1), is highlighted and placed within a structural context. The determination of the crystal structure of the membrane domain of human band 3, the founding member of the solute carrier 4 (SLC4) family of bicarbonate transporters, is a major breakthrough toward understanding the mechanism of action of this membrane transport protein, its interaction with partner proteins, and how mutations linked to disease affect its ability to fold and function. Band 3 contains 14 transmembrane segments arranged in a 7+7 transmembrane inverted repeat topology common to all members of the SLC4 family and the unrelated SLC26 anion transporter family. A functional feature of this fold is the presence of a core and a gate domain: the core domain contains two short transmembrane helices (TM3 and 10) that face each other in the middle of the membrane with the positive N-terminal helix dipoles creating the anion-binding site, whereas the gate domain forms the dimer interface. During transport, the movement of these two domains relative to each other provides the intracellular and extracellular compartments with alternating access to the central anion-binding site.

The Design of SCI‐57: An Ultrastable, Rapid‐acting, Single‐chain Insulin Analog

There are approximately 415 million people with Diabetes Mellitus worldwide and there exists a growing need for an ultrastable, heat resistant formulation of rapid‐acting insulin to treat the millions of people who live in developing countries where temperatures routinely exceed 45ºC. The heat resistance and stability of insulin is especially crucial due to the fact that insulin degrades ten times faster for every 10°C increase in temperature above 25°C. Several rapid‐acting insulin analogs have been created, though most do not last longer than 30 days and are reliant on the expensive cold chain delivery system of insulin analogs. This is due to chemical and physical degradation by way of deamidation, transamidation and cross‐beta assembly of linear polymers, or fibrillation. Rapid‐acting analogs must also combat the formation of the inactive hexameric formulation of insulin due to the presence of zinc and an excess of hydrogen ions. A single‐chain insulin analog has been created called SCI‐57 which consists of a glycine rich peptide (6 residues in length) that connects the A and B chains of the insulin analog. Adding a peptide tether will restrict splaying of the A and B chains, thus decreasing the risk of fibrillation even under high temperatures. To ensure that the analog is rapid‐acting and will not form storage hexamers, SCI‐57 has replaced ThrA8 with His to omit an unfavorable beta‐branched amino acid and HisB10 with Asp to create a more favorable relationship with the electrostatic dipole of the B‐chain alpha helix. Replacing HisB10 with Asp also blocks zinc binding, furthermore ensuring that the analog in its active, monomeric state. Both of these actions triple the activity of two‐chain analogs which will also benefit SCI‐57 by allowing it to bind quickly to the insulin receptor. Furthermore, SCI‐57 is much more resistant to fibrillation under high temperatures than previous analogs and maintains insulin receptor affinity as well as efficiency. The Nueva School MSOE Center for Biomolecular Modeling MAPS Team used 3‐D modeling and printing technology to examine structure‐function relationships of SCI‐57.Primary Citation:Hua, Qing‐xin, et al. “Design of an Active Ultrastable Single‐Chain Insulin Analog: SYNTHESIS, STRUCTURE, AND THERAPEUTIC IMPLICATIONS.” The Journal of Biological Chemistry, American Society for Biochemistry and Molecular Biology, 23 May 2008This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Gain Characteristic Maintained, Miniaturized LPDA Antenna Using Partially Applied Folded Planar Helix Dipoles

The miniaturization of a compact planar log-periodic dipole array (LPDA) antenna usually comes with a side effect of the gain deterioration phenomenon. To address this issue, a folded planar helix (FPH) dipole is designed as a miniaturized radiating element to replace parts of a conventional LPDA antenna composed of $\lambda /2$ dipoles in this paper. The FPH dipole has a radiation resistance and efficiency close to those of a $\lambda /2$ dipole with 39% reduced size and shows a higher radiation quality factor. The LPDA antenna with the longest $\lambda /2$ dipole replaced by the FPH element and the LPDA antenna with the longest and third-long $\lambda /2$ dipoles replaced by the FPH elements are examined. A conventional LPDA antenna can be miniaturized while avoiding gain degradation in the operation band of 400–800 MHz. The lowest impedance matched frequency and the frequency where the directional beam starts to appear are about the same for the proposed miniaturized LPDA antenna. Moreover, the front–back ratio can be improved by the proposed method. The prototype of the two-FPH-element applied LPDA antenna is built, and the design concept is verified experimentally. A size reduction of 39% and an average gain deterioration of −0.2 dB are achieved by the prototype in comparison with a conventional LPDA antenna. The proposed antenna can be utilized in the mobile radio wave direction-finding system.