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A macroscopically flexible inorganic nanofiber functional membrane.

Experimental implementations of optical multi-dimensional coherent spectroscopy (MDCS) are discussed in this chapter. The chapter starts with an overview of experimental approaches along with the general experimental requirements and considerations in implementing MDCS. Two specific approaches of using the actively stabilized box geometry and the phase modulated collinear geometry are discussed and compared. The last section discusses the analysis of experimental data for generating multi-dimensional spectra.

Basics of ultrafast spectroscopy are introduced in this chapter. We first discuss the basic concept of spectroscopy in terms of linear and nonlinear spectroscopy. We then describe definitions and parameters of ultrashort pulses and the ultrafast nonlinear/coherent spectroscopy. The density matrix formalism of light-matter interaction and the Bloch sphere representation of quantum states are also introduced.

An introduction to multidimensional coherent spectroscopy (MDCS) is provided in this chapter. We start out by introducing MDCS in qualitative terms, as an extension of transient absorption spectroscopy. We proceed to discuss the meaning and utility of coherent spectroscopy more generally. We go on to discuss the specifics of MDCS as a specific form of coherent spectroscopy. Pulse sequences involved in generating MDCS plots are introduced. Finally, we discuss density matrix perturbation theory and double-sided Feynman diagrams, and the role of this formalism in simulating and interpreting MDCS.

Interpretation of multi-dimensional coherent spectra is presented in this chapter. Results are presented with the Bloch model. We begin by discussing the characteristic features of an MDCS rephasing plot corresponding to a two-level system. We then discuss the characteristics of inhomogeneous ensembles of two-level systems. We go on to discuss the origins of cross-peaks in MDCS, and then some of the signatures in MDCS that arise as a result of many-body effects. Double-quantum spectra, zero-quantum spectra, three-dimensional spectra, and nonrephasing single-quantum spectra are discussed. Finally, we discuss the impact that finite pulse effects can have on a multidimensional spectrum.

New developments in implementation of optical multidimensional spectroscopy are presented. These include broadening the spectral range from terahertz to x-ray wavelengths, expanding the classes of materials that can be studied with the technique. Methods for improving the spatial resolution through, for example, tip-enhanced 2D spectroscopy, are discussed. Other methods for excitation and detection are present, including using non-classical light for excitation and detecting signals through photoemission of electrons.

Three-dimensional coherent spectroscopy techniques and experiments are presented in this chapter. The chapter begins with a discussion of different implementations of three-dimensional spectroscopy. The technique can be used to unravel contributions from different quantum pathways, providing a clear picture of the nonlinear response of complex systems. Application of the technique is discussed for three specific systems, including atomic vapors, semiconductor quantum wells, and light-harvesting complexes.

Two-dimensional spectroscopy experiments on atomically thin semiconductors, specifically transition metal dichalcogenides, are presented in this chapter. An introduction to 2D materials is given, followed by experiments measuring the homogeneous and inhomogeneous linewidth in 2D materials. Signature of exciton valley coherence and exciton-trion coherent coupling are revealed as unique spectral features in the spectra, which sheds light on the valley dephasing and relaxation processes in these materials.

Two-dimensional spectroscopy of a variety of semiconductor quantum dots is discussed in this chapter. The chapter begins with the optical and electronic properties of quantum dots. Experiments on three specific types of quantum dots are discussed, including GaAs interfacial fluctuation dots, self-assembled In(Ga)As dots including coherent control experiments, and colloidal dots.

Multidimensional coherent spectroscopy (MDCS) of atomic ensembles is discussed in this chapter. Atomic vapors such as potassium and rubidium atomic vapors are used a model system for demonstrating MDCS. The technique of MDCS can also be used to probe many-body dipole-dipole interaction and correlation in atoms by using double-quantum 2D spectroscopy. Multi-quantum 2D spectroscopy can detect many-body correlations associated with coherent states of multiple atoms in atoms.

Multi-dimensional coherent spectroscopy on a variety of materials and systems relevant to physics and materials science is discussed. This chapter provides a summary of results from material systems not already covered in previous chapters of the book. These include semiconductor carbon nanotubes, color centers in diamond, and perovskite materials. The technique elucidates several important features in each of these systems, including the homogeneous linewidths and dephasing processes, population relaxation channels and mechanisms, carrier redistribution dynamics, and coherent phonon interactions.

Two-dimensional coherent spectroscopy of semiconductor quantum wells is discussed in this chapter. The chapter starts with an introduction of semiconductor optics. The signatures of many-body interaction and correlation are revealed as spectral features in 2D spectra including one-, double-, and multi-quantum 2D spectra. Two-dimensional coherent spectroscopy can also be used to study the coupling in coupled quantum wells and exciton-polaritons in microcavities.

Optical multidimensional coherent spectroscopy provides information about the structure and excitation dynamics in a broad range of material systems. This book focuses on systems of interest in physics, including atomic vapors, semiconductor nanostructures and two-dimensional materials. An introduction to ultrafast spectroscopy and the fundamental concepts of multidimensional coherent spectroscopy applies to all material systems. Relevant experimental implementations, including phase-stabilized crossed-beams, frequency-tagged fully-collinear, three-dimensional and frequency-comb based methods. The use of the method to study atomic vapors, semiconductor quantum wells, semiconductor quantum dots and two-dimensional materials are described in separate chapters. The final chapters survey the use of the method in some other areas and speculate on future directions.

In this chapter a novel approach of multidimensional coherent spectroscopy is described. This approach uses multiple optical frequency combs and enables the measurement of comb resolution multidimensional coherent spectra in seconds. This chapter also shows how this new method can probe critical and fundamental processes in samples that have long dephasing times as well as can be used for practical applications such as chemical sensing and imaging.

The presence of sulfate groups in agar compromises the agar quality by affecting the crosslinking during gelling process. Some arylsulfatases can catalyze the hydrolysis of sulfate bonds in agar to improve the agar quality. Immobilized arylsulfatases prove beneficial advantages for their industrial applications. Here, a previously characterized mutant arylsulfatase K253H/H260L was immobilized on the synthesized magnetic Fe3O4 nanoparticles after functionalization by tannic acid (MNPs@TA). The surface properties and molecular structures of the immobilized arylsulfatase (MNPs@TA@ARS) were examined by scanning electron microscopy and Fourier transform infrared spectroscopy. Enzymatic characterization showed that MNPs@TA@ARS exhibited shifted optimal temperature and pH with deviated apparent Km and Vmax compared to its free counterpart. The immobilized arylsulfatase demonstrated improved thermal and pH stability and enhanced storage stability with modest reusability. In addition, MNPs@TA@ARS displayed enhanced tolerance to various inhibitors and detergents. The utilization of the immobilized arylsulfatase for agar desulfation brought the treated agar with improved quality.

Cell search is the first step to establish downlink synchronization between user equipment (UE) and base station (BS) in the fifth generation (5G) new radio (NR) system. However, frequency offset and noise will cause a massive loss of synchronization performance. To solve this problem, a novel timing synchronization algorithm of primary synchronization signal (PSS) with anti-frequency offset and anti-noise is proposed, which includes the improved coarse synchronization algorithm based on Fourier transform and the fine synchronization algorithm based on the triple auto-correlation algorithm. The improved coarse synchronization algorithm not only has a strong frequency offset resistance, especially for large frequency offset, but also obtains the estimated frequency offset. The fine synchronization algorithm is more resistant to noise than the conventional algorithm. Finally, the algorithm analysis and simulation results show that the improved algorithm can work very well even when the normalized frequency offset increases to greater than 0.8, but the conventional algorithm fails to synchronize properly. Meanwhile, when the SNR is as low as −6dB, the detection accuracy of the timing synchronization based on the proposed fine synchronization algorithm is improved by about 31.7% compared with the conventional algorithm.

Optical two-dimensional coherent spectroscopy (2DCS) has become a powerful tool for studying energy level structure, dynamics, and coupling in many systems including atomic ensembles. Various types of two-dimensional (2D) spectra, including the so-called single-quantum, zero-quantum, and double-quantum 2D spectra, of both D lines (D$_1$ and D$_2$ transitions) of potassium (K) atoms have been reported previously. For rubidium (Rb), a major difference is that the D-lines are about 15 nm apart as opposed to only about 3 nm for K. Simultaneously exciting both D-lines of Rb atoms requires a broader laser bandwidth for the experiment. Here, we report a broadband optical 2DCS experiment in an Rb atomic vapor. A complete set of single-quantum, zero-quantum, and double-quantum 2D spectra including both D-lines of Rb atoms were obtained. The experimental spectra were reproduced by simulated 2D spectra based on the perturbation solutions to the optical Bloch equations. This work in Rb atoms complements previous 2DCS studies of K and Rb with a narrower bandwidth that covers two D-lines of K or only a single D-line of Rb. The broadband excitation enables the capability to perform double-quantum and multi-quantum 2DCS of both D-lines of Rb to study many-body interactions and correlations in comparison with K atoms., Comment: 10 pages, 7 figures

The diverse biological activities of alginate oligosaccharides attracted extensive exploration of alginate lyases with various substrate specificity and enzymatic properties. In this study, an alginate lyase from Microbulbifer sp. ALW1, namely AlgL7, was phylogenetically classified into the polysaccharide lyase family 7 (PL7). The conserved amino acid residues Tyr606 and His499 in AlgL7 were predicted to act as the general acid/base catalysts. The enzyme was enzymatically characterized after heterologous expression and purification in E. coli. AlgL7 displayed optimal activity at 40 °C and pH 7.0. It had good stability at temperature below 35 °C and within a pH range of 5.0-10.0. AlgL7 exhibited good stability against the reducing reagent β-ME and the surfactants of Tween-20 and Triton X-100. The degradation profiles of alginate indicated AlgL7 was a bifunctional endolytic alginate lyase generating alginate oligosaccharides with the degrees of polymerization 2-4. The degradation products of sodium alginate exhibited stronger antioxidant activities than the untreated polysaccharide. In addition, AlgL7 could directly digest Laminaria japonica to produce alginate oligosaccharides. These characteristics of AlgL7 offer a great potential of its application in high-value utilization of brown algae resources.

Chondroitinase plays an important role in structural and functional studies of chondroitin sulfate (CS). In this study, a new member of chondroitinase B of PL6 family, namely ChSase B6, was cloned from marine bacterium Microbulbifer sp. ALW1 and subjected to enzymatic and structural characterization. The recombinant ChSase B6 showed optimum activity at 40 °C and pH 8.0, with enzyme kinetic parameters of Km and Vmax against chondroitin sulfate B (CSB) to be 7.85 µg/mL and 1.21 U/mg, respectively. ChSase B6 demonstrated thermostability under 60 °C for 2 h with about 50% residual activity and good pH stability under 4.0–10.0 for 1 h with above 60% residual activity. In addition, ChSase B6 displayed excellent stability against the surfactants including Tween-20, Tween-80, Trion X-100, and CTAB. The degradation products of ChSase B6-treated CSB exhibited improved antioxidant ability as a hydroxyl radical scavenger. Structural analysis and site-directed mutagenesis suggested that the conserved residues Lys248 and Arg269 were important for the activity of ChSase B6. Characterization, structure, and molecular dynamics simulation of ChSase B6 provided a guide for further tailoring for its industrial application for chondroitin sulfate bioresource development.

Collective resonance of interacting particles has important implications in many-body quantum systems and their applications. Strong interactions can lead to a blockade that prohibits the excitation of a collective resonance of two or more nearby atoms. However, a collective resonance can be excited with the presence of weak interaction and has been observed for atoms in the first excited state ($P$ states). Here, we report the observation of collective resonance of rubidium atoms in a higher excited state ($D$ states) in addition to the first excited state. The collective resonance is excited by a double-quantum four-pulse excitation sequence. The resulting double-quantum two-dimensional (2D) spectrum displays well-isolated peaks that can be attributed to collective resonances of atoms in $P$ and $D$ states. The experimental one-quantum and double-quantum 2D spectra can be reproduced by a simulation based on the perturbative solutions to the optical Bloch equations, confirming collective resonances as the origin of the measured spectra. The experimental technique provides a new approach for preparing and probing collective resonances of atoms in highly excited states., Comment: 8 pages, 5 figures

Alginate lyases can depolymerize alginate to oligomers with potential applications in many fields. Here a new alginate lyase, namely AlgL6, was characterized from Microbulbifer sp. ALW1, phylogenetically classified into the polysaccharide lyase family 6 (PL6). The recombinant alginate lyase AlgL6 exerted enzymatic activities towards polymannuronate, polyguluronate, and sodium alginate in an exolytic manner. AlgL6 had an optimum temperature of 35 °C and good stability at 30 °C or below. Its optimum pH was 8.0, and it had good stability over the pH range of 5.0-9.0. AlgL6 exhibited excellent halo-stability against Na

We report a novel, to the best of our knowledge, double-quantum–zero-quantum two-dimensional coherent spectroscopy (2DCS) that allows direct detection of the quantum coherence between multiparticle collective states. Through correlating the double-quantum coherence and the zero-quantum coherence, signatures for coherence between collective states can be well isolated as side peaks and readily identified in the 2D spectrum. The experiment is implemented in a vapor of rubidium atoms in a collinear 2DCS setup. Good agreement with a theoretical simulation using density matrix confirms the essential role of the interatomic correlation effect in generating the side peak signals. This 2D spectrum technique paves a new avenue for studying the coherent coupling of highly excited states and many-body properties.

We report an experimental demonstration of optical 2DCS in cold atoms. The experiment integrates a collinear 2DCS setup with a magneto-optical trap (MOT), in which cold rubidium (Rb) atoms are prepared at a temperature of about 200 $\mu$K and a number density of $10^{10}$ cm$^{-3}$. With a sequence of femtosecond laser pulses, we first obtained one-dimensional second- and fourth-order nonlinear signals and then acquired both one-quantum and zero-quantum 2D spectra of cold Rb atoms. The capability of performing optical 2DCS in cold atoms is an important step toward optical 2DCS study of many-body physics in cold atoms and ultimately in atom arrays and trapped ions. Optical 2DCS in cold atoms/molecules can also be a new avenue to probe chemical reaction dynamics in cold molecules., Comment: 5 pages, 4 figures

A new alginate lyase gene of algl17 was cloned from an alginate-degrading marine bacterium Microbulbifer sp. ALW1. The gene contained 2220 bp and encoded a 739-amino acid protein classified into the PL-17 family. The recombinant alginate lyase AlgL17 was overexpressed and purified from Escherichia coli BL21 (DE3) with a molecular mass of 84.9 kDa. This enzyme showed activities towards sodium alginate, polyM and alginate oligosaccharide, but very low activity towards polyG. These results indicate that AlgL17 is a polyM-specific oligoalginate lyase. When sodium alginate was used as a substrate, the optimum reaction temperature and pH for the enzyme were 35 °C and pH 8.0, respectively. Recombinant AlgL17 was stable at 25 °C, but not stable at 30 °C and 35 °C. It showed good stability over a pH range of 5.0–8.0. The enzyme activity was increased to 1.7 times by adding NaCl to a final concentration of 0.7 M. The ability of the recombinant AlgL17 producing 4-deoxy-L-erythro-5-hexoseulose uronic acid (DEH) from sodium alginate and polyM block indicates that AlgL17 is an exo-type alginate lyase.

This study aimed to improve the thermostability of arylsulfatase from Pseudoalteromonas carrageenovora. A library of P. carrageenovora arylsulfatase mutants was constructed by introducing random mutagenesis using error-prone PCR. After screening, two mutants of H260L and D84A/H260L showed enhanced thermal stability than the wild-type predecessor (WT). Site-directed mutagenesis demonstrated that only amino acid residue at Position 260 plays an important role in the thermostability of P. carrageenovora arylsulfatase. Thermal inactivation analysis showed that the half-life (t1/2) values at 55°C for H260L, H260I, H260Q, H260F and H260R were 40.6, 48.4, 30.9, 29.1 and 34.5 min, respectively, while that of WT was 9.1 min. Structure modeling demonstrated that the additional hydrogen bonds and/or optimization of surface charge-charge interactions could be responsible for the increased thermostability imparted by H260L, H260I, H260Q, H260F and H260R.

An agarase gene containing 1 302 bp was cloned from Microbulbifer sp. AG1. It encoded a mature protein of 413 amino acids plus a 20-residue signal peptide. The recombinant enzyme without the signal peptide was expressed and purified from Escherichia coli BL21 (DE3). When agarose was used as a substrate, the optimal temperature and pH for the enzyme were 60°C and 7.5, respectively. The recombinant agarase showed excellent thermostability with 67% and 19% of residual activities after incubation at 50°C and 60°C for 1 h, respectively. Except SDS, the recombinant agarase had a relatively good resistance against the detected inhibitors, detergents and urea denaturant. Thin layer chromatography analysis and enzyme assay using p-nitrophenyl-α/β-Dgalactopyranoside revealed that the recombinant agarase was a β-agarase that degraded agarose into neoagarotetraose as the main end product. The enzymatic hydrolysis products with different degree of polymerization exhibited the antioxidant activities.

For most three centuries after Hooke introduced optical microscopy, refinement of the instrumentation made microscopes more convinient than anything else. As in modern microscopy, a light source, an objective lens, and an eyepiece were used to project an image magnified from a 100-fold to 1,000-fold into a human eye. This range of magnifications and resolution (of the order of 200 nm) has brought cellular morphology and tissue structure into view and made optical microscopy the perfect partner for biological investigations. A resolution constraint in optical imaging is imposed by the diffraction limit discovered by Lord Rayleigh in the 19th century. Fundamentally, this restricts the ability to resolve two distant point sources, such as stars or planets, with an angular resolution α smaller than the wavelength of light λ divided by the numerical aperture of the imaging system

The bacterium Microbulbifer sp. ALW1 was previously characterized with the capability to break down the cell wall of brown algae into fine pieces. The biological functions of strain ALW1 were yet to be elucidated. In this study, a gene, namely MaCel5A, was isolated from the ALW1 strain genome, encoding an endo-β-1,4-glucanase. MaCel5A was phylogenetically categorized under the glycoside hydrolase family GH5, with the highest identity to a putative cellulase of Microbulbifer thermotolerans. The recombinant MaCel5A protein purified from heterologous expression in E. coli exhibited maximum activity at 50 °C and pH 6.0, respectively, and functioned selectively toward carboxymethyl cellulose and barley β-glucan. Recombinant MaCel5A demonstrated considerable tolerance to the exposure to high temperature up to 80 °C for 30 min retaining 49% residual activity. In addition, MaCel5A showed moderate stability against pH 5.0–11.0 and strong stability in the presence of nonionic surfactant. MaCel5A exhibited strong halo-stability and halotolerance. The activity of the enzyme increased about tenfold at 0.5 M NaCl, and about fivefold even at 4.0 M NaCl compared to the enzyme activity without the addition of salt. The two conserved glutamic acid residues in MaCel5A featured the typical catalytic acid/base and nucleophile machinery of glycoside hydrolases. These characteristics highlight the industrial application potential of MaCel5A.

Glucose-tolerant and/or glucose-stimulated β-glucosidase is of great interest for its industrial utilization in enzymatic digestion of lignocellulosic biomass for biofuel production. In this study, a new gene of β-glucosidase MaGlu1A was cloned from an alginate-degrading marine bacterium Microbulbifer sp. ALW1. The gene of MaGlu1A encoded a 472-amino acid protein classified into the glycosyl hydrolase family 1 (GH1). The recombinant β-glucosidase was overexpressed and purified from Escherichia coli with a molecular mass of 65.0 kDa. Structure analysis illustrated the catalytic acid/base residue Glu186 and nucleophilic residue Glu370 in the enzyme. MaGlu1A displayed optimal activity at 40 °C and pH 4.5, respectively. It had substrate preference to the aryl-β-glycosidic bonds with glucose, fucose, and galactose moieties, in addition to cellobiose. MaGlu1A demonstrated strong stimulation to the supplemental glucose. Site-directed mutagenesis suggested an essential role of Asn242 in glucose stimulation. The enzymatic characterization of MaGlu1A provides general information about its catalytic properties facilitating its practical applications.

We performed two-dimensional coherent spectroscopy of photoexcited carriers in methylammonium lead iodide perovskite at room temperature. The 2D spectra revealed ultrafast dynamics of two resonances which can be attributed to hot carriers and excitons.

Spontaneous emission from individual atoms in vapor lasts nanoseconds, if not microseconds, and beatings in this emission involve only directly excited energy sublevels. In contrast, the superfluorescent emissions burst on a much-reduced timescale and their beatings involve both directly and indirectly excited energy sublevels. In this work, picosecond and femtosecond superfluorescent beatings are observed from a dense cesium atomic vapor. Cesium atoms are excited by 60-femtosecond long, 800 nm laser pulses via two-photon processes into their coherent superpositions of the ground 6S and excited 8S states. As a part of the transient four wave mixing process, the yoked superfluorescent blue light at lower transitions of 6S - 7P are recorded and studied. Delayed buildup time of this blue light is measured as a function of the input laser beam power using a high-resolution 2 ps streak camera. The power dependent buildup delay time is consistently doubled as the vapor temperature is lowered to cut the number of atoms by half. At low power and density, a beating with a period of 100 picoseconds representing the ground state splitting is observed. The autocorrelation measurements of the generated blue light exhibit a beating with a quasi-period of 230 fs corresponding to the splitting of the 7P level primarily at lower input laser power. Understanding and, eventually, controlling the intriguing nature of superfluorescent beatings may permit a rapid quantum operation free from the rather slow spontaneous emission processes from atoms and molecules., Comment: 7 pages, 5 figures

We developed a frequency-domain model describing optical frequency-comb generation in optical resonators with second- and third-order nonlinearities. Compared with time-domain models, our model in principle allows one to express the cavity dispersion accurately, avoiding the dispersion being truncated beyond a certain order. Moreover, the frequency-domain model can readily include frequency dependence of system parameters, such as the linear absorption and the cavity coupling ratio. To demonstrate the validity of our model, we numerically simulated quadratic combs in a singly resonant second-harmonic generation cavity and Kerr combs in a micro-resonator as two examples. The simulated results obtained from the frequency-domain model agree well with those given by previous time-domain models. A system containing both second- and third-order nonlinearities can give rise to many novel physical dynamics. The developed frequency-domain model will contribute to understanding optical frequency-comb generation assisted by multi-order nonlinear processes in various optical resonators., 8 pages, 4 figures

As optical two-dimensional coherent spectroscopy (2DCS) is extended to a broader range of applications, it is critical to improve the detection sensitivity of optical 2DCS. We developed a fast phase-cycling scheme in a non-collinear optical 2DCS implementation by using liquid crystal phase retarders to modulate the phases of two excitation pulses. The background in the signal can be eliminated by combining either two or four interferograms measured with a proper phase configuration. The effectiveness of this method was validated in optical 2DCS measurements of an atomic vapor. This fast phase-cycling scheme will enable optical 2DCS in novel emerging applications that require enhanced detection sensitivity., 4 pages, 3 figures, 1 table

The presence of sulfate groups in agar compromises the agar quality by affecting the crosslinking during gelling process. Some arylsulfatases can catalyze the hydrolysis of sulfate bonds in agar to improve the agar quality. Immobilized arylsulfatases prove beneficial advantages for their industrial applications. Here, a previously characterized mutant arylsulfatase K253H/H260L was immobilized on the synthesized magnetic Fe3O4 nanoparticles after functionalization by tannic acid (MNPs@TA). The surface properties and molecular structures of the immobilized arylsulfatase (MNPs@TA@ARS) were examined by scanning electron microscopy and Fourier transform infrared spectroscopy. Enzymatic characterization showed that MNPs@TA@ARS exhibited shifted optimal temperature and pH with deviated apparent Km and Vmax compared to its free counterpart. The immobilized arylsulfatase demonstrated improved thermal and pH stability and enhanced storage stability with modest reusability. In addition, MNPs@TA@ARS displayed enhanced tolerance to various inhibitors and detergents. The utilization of the immobilized arylsulfatase for agar desulfation brought the treated agar with improved quality., An arylsulfatase of marine bacterial origin was immobilized on the magnetic nanobeads. The immobilized arylsulfatase had enhanced thermal and pH stability. After treatment of agar by the immobilized enzyme, agar had equivalent quality to agarose.

Alginate is a natural polysaccharide resource abundant in brown algae and it can be cleaved into alginate oligosaccharides by alginate lyase. Alginate lyases and the bioactive alginate oligosaccharides have been applied in diverse fields such as pharmaceutical therapy and nutraceutical supplementation. Immobilized enzymes greatly facilitate their industrial application owing to their reusability, stability, and tunability. In this study, magnetic Fe3O4 nanoparticles were synthesized and used to immobilize an exolytic alginate lyase AlgL17 that was characterized previously. The immobilized AlgL17 demonstrated enhanced thermal and pH tolerance, extended storage stability, and moderate reusability. The mass spectrum indicated the specific activity of the immobilized AlgL17 to release alginate oligosaccharides (AOS) from alginate polysaccharide. The produced AOS exhibited their antioxidant and antiapoptotic activities in H2O2-stressed human umbilical vein endothelial cells by upregulation of reactive oxygen species scavenging activities and attenuation of the caspase-mediated apoptosis pathway.