Surface-enhanced Raman scattering measurement from a lipid bilayer encapsulating a single decahedral nanoparticle mediated by an optical trap

We present a new technique for the study of model membranes on the length-scale of a single nanosized liposome. Silver decahedral nanoparticles have been encapsulated by a model unilamellar lipid bilayer creating nano-sized lipid vesicles. The metal core has two roles (i) increasing the polarizability of vesicles, enabling a single vesicle to be isolated and confined in an optical trap, and (ii) enhancing Raman scattering from the bilayer, via the high surface-plasmon field at the sharp vertices of the decahedral particles. Combined this has allowed us to measure a Raman fingerprint from a single vesicle of 50 nmdiameter, containing just ∼104 lipid molecules in a bilayer membrane over a surface area of <0.01 µm2, equivalent to a volume of approximately 1 zepto-litre. Raman scattering is a weak and inefficient process and previous studies have required either a substantially larger bilayer area in order to obtain a detectable signal, or the tagging of lipid molecules with a chromophore to provide an indirect probe of the bilayer. Our approach is fully label-free and bio-compatible and, in the future, it will enable much more localized studies of the heterogeneous structure of lipid bilayers and of membrane-bound components than is currently possible

Raman spectroscopy of supported lipid bilayers and membrane proteins

Off-resonance unenhanced total internal reflection (TIR) Raman Spectroscopy was explored to investigate supported single lipid bilayers with incorporated membrane peptides/proteins at water/solid interface. A model membrane was formed on a planar supported lipid layer (pslb) by the fusion of the reconstituted small unilamellar vesicles (SUVs), and the intensity of bilayer was confirmed by a comparison of Raman spectral intensity in the C-H stretching modes with C16TAB. With prominent Raman sensitivity attained, we studied the 2-D phase transition of DMPC and DPPC pslbs and the temperature-dependent polarised spectra revealed a broad transition range of ca. 10 °C commencing at the calorimetric phase transition temperature. We applied polarised TIR-Raman Spectroscopy to pslbs formed by DMPC SUVs reconstituted with a model membrane-spanning peptide gramicidin D. A preferential channel structure formed by dissolution of trifluoroethanol could be probed by polarised Raman Spectroscopy qualitatively showing an antiparallel β-sheet conformation (different from "standard" one) and our Raman spectra by correlation with NMR and CD data confirmed single-stranded π6.3 β-helical channel structure in the single bilayer. We also studied the membrane-penetrating peptide indolicidin in the presence of DMPC pslb over the chain melting temperature and a β-turn structure was dominantly observed concomitant with membrane perturbation. Dynamic adsorption of DPPC to form pslb from a micellar solution of n-dodecyl-β- D-maltoside could be examined with high sensitivity of every 1-min acquisition. Finally we used polarised TIR-Raman scattering to porcine pancreatic phospholipase A2 hydrolytic activity on DPPC pslbs and revealed lipid-active conformation different from that of the enzyme alone.</p

Raman spectroscopy of supported lipid bilayers and membrane proteins

Off-resonance unenhanced total internal reflection (TIR) Raman Spectroscopy was explored to investigate supported single lipid bilayers with incorporated membrane peptides/proteins at water/solid interface. A model membrane was formed on a planar supported lipid layer (pslb) by the fusion of the reconstituted small unilamellar vesicles (SUVs), and the intensity of bilayer was confirmed by a comparison of Raman spectral intensity in the C-H stretching modes with C16TAB. With prominent Raman sensitivity attained, we studied the 2-D phase transition of DMPC and DPPC pslbs and the temperature-dependent polarised spectra revealed a broad transition range of ca. 10 °C commencing at the calorimetric phase transition temperature. We applied polarised TIR-Raman Spectroscopy to pslbs formed by DMPC SUVs reconstituted with a model membrane-spanning peptide gramicidin D. A preferential channel structure formed by dissolution of trifluoroethanol could be probed by polarised Raman Spectroscopy qualitatively showing an antiparallel β-sheet conformation (different from "standard" one) and our Raman spectra by correlation with NMR and CD data confirmed single-stranded π6.3 β-helical channel structure in the single bilayer. We also studied the membrane-penetrating peptide indolicidin in the presence of DMPC pslb over the chain melting temperature and a β-turn structure was dominantly observed concomitant with membrane perturbation. Dynamic adsorption of DPPC to form pslb from a micellar solution of n-dodecyl-β- D-maltoside could be examined with high sensitivity of every 1-min acquisition. Finally we used polarised TIR-Raman scattering to porcine pancreatic phospholipase A2 hydrolytic activity on DPPC pslbs and revealed lipid-active conformation different from that of the enzyme alone.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Raman spectra of planar supported lipid bilayers

AbstractRaman scattering has been used to obtain high quality vibrational spectra of planar supported lipid bilayers (pslb's) at the silica/water interface without the use of resonance or surface enhancement. A total internal reflection geometry was used both to increase the bilayer signal and to suppress the water background. Polarization control permits the determination of four components of the Raman tensor, of which three are independent for a uniaxial film. Spectra are reported of the phospholipids DMPC, DPPC, and POPC, in the C–H stretching region and the fingerprint region. The temperature-dependent polarized spectra of POPC show only small changes over the range 14–41 °C. The corresponding spectra of DMPC and DPPC bilayers show large thermal changes consistent with a decreasing tilt angle from the surface normal and increasing chain ordering at lower temperatures. The thermal behavior of DMPC pslb's is similar to that of vesicles of the same lipid in bulk suspension. In contrast to calorimetry, which shows a sharp phase transition (Lα–Lβ') with decreasing temperature, the changes in the Raman spectra occur over a temperature range of ca. 10 °C commencing at the calorimetric phase transition temperature

Comparative Study of 1444 nm Laser Monotherapy versus Integrated Liposuction in the Treatment of Axillary Osmidrosis

Background and Objectives: The 1444 nm wavelength Neodymium:Yttrium–Aluminum–Garnet (Nd:YAG) laser treatment is an efficient method for treating axillary osmidrosis (AO); however, it has a relatively low treatment persistence. To address this issue, we performed integrated liposuction surgery with a laser to treat AO and compared the results with those of a group treated only with a laser. Materials and Methods: This study compared the outcomes of AO treatment between the two groups up to six months postoperatively. The first group of 18 patients underwent laser treatment alone, and the second group of 12 patients underwent integrated liposuction surgery in addition to laser treatment. Outcomes were assessed using the following variables: degree of malodor (DOM), sweating area, patient satisfaction, pain levels, and complications, such as burns, swelling, and contractures. Results: Compared to the laser-only group, the integrated liposuction group demonstrated significantly superior outcomes in terms of DOM (p = 0.002) and patient satisfaction (p = 0.006), as well as a reduction in the sweating area (p = 0.012). The pain rating was higher in the liposuction group, but the difference was not statistically significant (p = 0.054). Compared with the patients in the integrated liposuction treatment group, those in the laser treatment group exhibited a significantly higher number of burns under the axillae (p = 0.025). However, no significant differences were observed in the swelling or contracture between the groups. Conclusions: Integrated liposuction with laser therapy significantly improved treatment outcomes, including malodor, patient satisfaction, sweat test results, and decreased complication rates

Raman spectroscopy of supported lipid bilayers and membrane proteins

Off-resonance unenhanced total internal reflection (TIR) Raman Spectroscopy was explored to investigate supported single lipid bilayers with incorporated membrane peptides/proteins at water/solid interface. A model membrane was formed on a planar supported lipid layer (pslb) by the fusion of the reconstituted small unilamellar vesicles (SUVs), and the intensity of bilayer was confirmed by a comparison of Raman spectral intensity in the C-H stretching modes with C16TAB. With prominent Raman sensitivity attained, we studied the 2-D phase transition of DMPC and DPPC pslbs and the temperature-dependent polarised spectra revealed a broad transition range of ca. 10 °C commencing at the calorimetric phase transition temperature. We applied polarised TIR-Raman Spectroscopy to pslbs formed by DMPC SUVs reconstituted with a model membrane-spanning peptide gramicidin D. A preferential channel structure formed by dissolution of trifluoroethanol could be probed by polarised Raman Spectroscopy qualitatively showing an antiparallel β-sheet conformation (different from "standard" one) and our Raman spectra by correlation with NMR and CD data confirmed single-stranded π6.3 β-helical channel structure in the single bilayer. We also studied the membrane-penetrating peptide indolicidin in the presence of DMPC pslb over the chain melting temperature and a β-turn structure was dominantly observed concomitant with membrane perturbation. Dynamic adsorption of DPPC to form pslb from a micellar solution of n-dodecyl-β- D-maltoside could be examined with high sensitivity of every 1-min acquisition. Finally we used polarised TIR-Raman scattering to porcine pancreatic phospholipase A2 hydrolytic activity on DPPC pslbs and revealed lipid-active conformation different from that of the enzyme alone.</p

A 1-v 4.6-mw/channel fully differential neural recording front-end ic with current-controlled pseudoresistor in 0.18-mm cmos

This paper presents a fully differential implantable neural recording front-end IC for monitoring neural activities. Each analog front-end (AFE) consists of a low-noise amplifier (LNA), a variable gain amplifier (VGA), and a buffer. The output signal of the AFE is digitized through a successive approximation register analog-to-digital converter (SAR ADC). The LNA adopts the current-reuse technique to improve the current efficiency, achieving the power consumption as low as 0.95 mW. The implemented LNA has the gain of 40 dB, the low-pass cutoff frequency of 10 kHz, and the high-pass cutoff frequency of sub-1 Hz which is realized using the current-controlled pseudoresistor. The VGA controls the gain from 21.9 dB to 33.9 dB for efficient digitization while consuming the power of 0.35 mW. The buffer drives the capacitive DAC of the ADC and consumes the power of 3.28 mW. The fabricated AFE occupies the area of 0.11 mm 2 /Channel and consumes 4.6 mW/Channel under 1-V supply voltage. Each channel achieves the input-referred noise of 2.88 mV rms , the NEF of 2.38, and the NEF 2 V DD of 5.67. The front-end IC is implemented in a standard 1P6M 0.18-mm CMOS process. © 2019, Institute of Electronics Engineers of Korea. All rights reserved.1

A 118.6fJ/Conversion-Step Two-Step Time-Domain RC-to-Digital Converter With 33nF/10MΩ Range and 53aFrmsResolution

Sensor readout ICs for internet-of-things (IoT) systems require not only high energy efficiency and resolution but also a wide input range to cover a variety of sensors with different output types and characteristics [1], [2]. Readout methods based on delta-sigma modulation (DSM) [3], [4] and two-step conversion (successive approximation + time-domain (TD) DSM) [5] have been proposed to achieve high resolution and energy efficiency, but these structures suffer from limited input ranges as they convert the sensor output to voltage, whose range is strictly constrained by the given supply rails. Alternatively, a TD readout method converts the sensor output into a TD signal, eliminating the range constraint [1], [2], [6]. However, its resolution is limited by the jitter performance of the oscillator of the counting clock [1]. This resolution issue can be addressed together with a wide input range by a dual-oscillator-based structure utilizing a large oversampling ratio (OSR) [2]. However, a power-hungry high-frequency reference oscillator (R-OSC) should continuously operate to reduce the quantization noise (Q-noise), degrading energy efficiency greatly. Although this structure can reduce both the Q-noise and random noise by sacrificing the readout time, the signal-to-noise ratio (SNR) per energy efficiency is limited by the performance of the oscillator itself. Here, we present a TD 2-stepconversion readout IC achieving a wide input range, high resolution, and high energy efficiency altogether. © 2022 IEEE