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Acute physiological responses to combined blood flow restriction and low-level laser
摘要： Purpose Blood flow restriction (BFR) is an innovation in fitness to train muscles with low loads at low oxygen levels. Low-level laser therapy (LLLT) is a bio-energetic approach to alleviate muscle fatigue during resistance training. This study investigated the immediate effect of LLLT pre-conditioning on BFR that accelerates muscle fatigue due to ischemia. Methods Fifteen young adults participated in this study of a crossover randomized design. They completed a low-load contraction with various pre-conditioning (blood flow restriction with low-level laser therapy (LLLT + BFR), blood flow restriction with sham low-level laser therapy (BFR), and control). Force fluctuation dynamics, muscle oxygen saturation of hemoglobin and myoglobin (SmO2), and discharge patterns of motor units (MU) were compared. Results Normalized SmO2 during low-load contractions significantly varied with the pre-contraction protocols (Control (83.6 ± 3.0%) > LLLT + BFR (70.3 ± 2.8%) > BFR (55.4 ± 2.4%). Also, force fluctuations and MU discharge varied with the pre-contraction protocols. Multi-scale entropy and mean frequency of force fluctuations were greater in the LLLT + BFR condition (31.95 ± 0.67) than in the BFR condition (29.47 ± 0.73). The mean inter-spike interval of MUs was greater in the LLLT + BFR condition (53.32 ± 2.70 ms) than in the BFR condition (45.04 ± 1.08 ms). In particular, MUs with higher recruitment thresholds exhibited greater LLLT-related discharge complexity (LLLT + BFR (0.201 ± 0.012) > BFR (0.154 ± 0.006)). Conclusions LLLT pre-conditioning can minimize the BFR-related decline in muscle oxygen saturation, leading to force gradation and MU discharge in a cost-effective and complex manner.
关键词： Myoglobin,Motor unit,Force fluctuations,Electromyography,Photobiomodulation,Hypoxia
更新于2025-09-23 15:19:57
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SERS-Active Substrates Nanoengineering Based on e-Beam Evaporated Self-Assembled Silver Films
摘要： Surface-enhanced Raman spectroscopy (SERS) has been intensely studied as a possible solution in the fields of analytical chemistry and biosensorics for decades. Substantial research has been devoted to engineering signal enhanced SERS-active substrates based on semi-continuous nanostructured silver and gold films, or agglomerates of micro- and nanoparticles in solution. Herein, we demonstrate the high-amplitude spectra of myoglobin precipitated out of ultra-low concentration solutions (below 10 μg/mL) using e-beam evaporated continuous self-assembled silver films. We observe up to 105 times Raman signal amplification with purposefully designed SERS-active substrates in comparison with the control samples. SERS-active substrates are obtained by electron beam evaporation of silver thin films with well controlled nanostructured surface morphology. The characteristic dimensions of the morphology elements vary in the range from several to tens of nanometers. Using optical confocal microscopy we demonstrate that proteins form a conformation on the surface of the self-assembled silver film, which results in an effective enhancement of giant Raman scattering signal. We investigate the various SERS substrates surface morphologies by means of atomic force microscopy (AFM) in combination with deep data analysis with Gwyddion software and a number of machine learning techniques. Based on these results, we identify the most significant film surface morphology patterns and evaporation recipe parameters to obtain the highest amplitude SERS spectra. Moreover, we demonstrate the possibility of automated selection of suitable morphological parameters to obtain the high-amplitude spectra. The developed AFM data auto-analysis procedures are used for smart optimization of SERS-active substrates nanoengineering processes.
关键词： metal film,neural networks,myoglobin,SERS substrate,e-beam evaporation
更新于2025-09-12 10:27:22
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Protective characterization of low dose sodium nitrite on yak meat myoglobin in a hydroxy radical oxidation environment: Fourier Transform Infrared spectroscopy and laser Micro-Raman spectroscopy
摘要： The effect of NaNO2 in hydroxyl radical-mediated oxidative damage of yak meat myoglobin was investigated. Laser micro-Raman spectroscopy and Fourier Transform Infrared spectroscopy were used to assess protein (carbonyls, total sulfhydryl and Disulfide bonds) oxidation, atomic (or molecular) interactions and secondary structural changes. The addition of NaNO2 during the oxidation of myoglobin significantly reduced the content of carbonyl and disulfide bonds and protected the sulfhydryl groups from hydroxyl radical oxidation (P < 0.05). There was no significant difference in the secondary structure of myoglobin between the control group and the SN treatment group(P > 0.05). At the same time, NaNO2 had an inhibitory effect on the expansion of the hemoglobin center size and the transition of Fe from a low spin state to a high spin state caused by radical-oxidized. These findings suggest that NaNO2 has potential for treatment effects in a hydroxyl radical-oxidized myoglobin.
关键词： Secondary structure,Hydroxyl radical,Raman spectroscopy,NaNO2,Myoglobin
更新于2025-09-11 14:15:04
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Photoexcitation Dynamics of Thiocyanate-Bound Heme Proteins Using Femtosecond Infrared Spectroscopy
摘要： Myoglobin (Mb) and hemoglobin (Hb) have been used as model systems to understand the relationships between protein function, structure, and dynamics. These studies have primarily been carried out by observing the (re)binding between ferrous heme proteins and neutral ligands. Ferric heme proteins also bind to various anionic ligands, such as CN?, N3?, OCN?, and SCN?. Only a few anion-bound ferric heme proteins have been investigated for ligand-binding dynamics.1–4 Although CN?-bound Mb (MbCN) was reported to be photostable, i.e., not photodeligated by a visible photon, recent study using Raman spectroscopy claimed a photodeligation quantum yield for MbCN of 0.75.5 Thus, the photostability of ?-bound MbCN is still in question. At room temperature, N3?-bound Mb (MbN3) exists in both high spin (HS) and low spin (LS) complexes. When MbN3 absorbs a visible photon, the ligand is not dissociated; instead the excited MbN3 undergoes a thermal relaxation process involving a spin transition.3 Recently, we have shown that photoexcited OCN?-bound Mb and OCN?-bound Hb are also photostable, losing their excess energy via thermal relaxation after rapid electronic relaxation.4 Here, to determine the general excitation properties of anion-bound heme proteins after absorption of a visible photon, we have extended our study of photoexcitation dynamics to SCN?-bound ferric Mb (MbNCS) and Hb (HbNCS).
关键词： Femtosecond vibrational spectroscopy,Thiocyanate-bound myoglobin,Electronic relaxation,Ferric heme proteins,Thermal relaxation
更新于2025-09-10 09:29:36
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Ultrafast carbon monoxide photolysis and heme spin-crossover in myoglobin via nonadiabatic quantum dynamics
摘要： Light absorption of myoglobin triggers diatomic ligand photolysis and a spin crossover transition of iron(II) that initiate protein conformational change. The photolysis and spin crossover reactions happen concurrently on a femtosecond timescale. The microscopic origin of these reactions remains controversial. Here, we apply quantum wavepacket dynamics to elucidate the ultrafast photochemical mechanism for a heme–carbon monoxide (heme–CO) complex. We observe coherent oscillations of the Fe–CO bond distance with a period of 42 fs and an amplitude of ～1 ?. These nuclear motions induce pronounced geometric reorganization, which makes the CO dissociation irreversible. The reaction is initially dominated by symmetry breaking vibrations inducing an electron transfer from porphyrin to iron. Subsequently, the wavepacket relaxes to the triplet manifold in ～75 fs and to the quintet manifold in ～430 fs. Our results highlight the central role of nuclear vibrations at the origin of the ultrafast photodynamics of organometallic complexes.
关键词： Ultrafast carbon monoxide photolysis,nonadiabatic quantum dynamics,myoglobin,heme spin-crossover
更新于2025-09-09 09:28:46