Complex amplitude modulated holographic display system based on polarization grating.

We propose a holographic display system for complex amplitude modulation (CAM) using a phase-only spatial light modulator (SLM) and two polarization gratings (PG). The two sub-holograms of the complex-amplitude computed generated hologram (CGH) are loaded in different regions of SLM. Two diffractive components couple in space after longitudinal migration from the double PGs, and finally interfered through the line polarizer. The influence of the system error on the reconstructed image quality is analyzed, which provides a theoretical assessment for adding pre-compensation to CGH to compensate the system error. Moreover, on the base of the proposed system, a large depth of field and enlarged display area display is realized and the real-time display can be achieved because of the analytical complex-amplitude computed generated hologram. The optical experimental results show that the proposed system has high energy efficiency, and can provide high-quality holographic display with a large depth of field and enlarged display area.

End-to-end real-time holographic display based on real-time capture of real scenes.

Holographic display is considered as a promising three-dimensional (3D) display technology and has been widely studied. However, to date, the real-time holographic display for real scenes is still far from being incorporated in our life. The speed and quality of information extraction and holographic computing need to be further improved. In this paper, we propose an end-to-end real-time holographic display based on real-time capture of real scenes, where the parallax images are collected from the scene and a convolutional neural network (CNN) builds the mapping from the parallax images to the hologram. Parallax images are acquired in real time by a binocular camera, and contain depth information and amplitude information needed for 3D hologram calculation. The CNN, which can transform parallax images into 3D holograms, is trained by datasets consisting of parallax images and high-quality 3D holograms. The static colorful reconstruction and speckle-free real-time holographic display based on real-time capture of real scenes have been verified by the optical experiments. With simple system composition and affordable hardware requirements, the proposed technique will break the dilemma of the existing real-scene holographic display, and open up a new direction for the application of real-scene holographic 3D display such as holographic live video and solving vergence-accommodation conflict (VAC) problems for head-mounted display devices.

A Novel Method for γ-Aminobutyric Acid Biosynthesis Using Glutamate Decarboxylase Entrapped in Polyvinyl Alcohol-Sodium Alginate Capsules.

γ-aminobutyric acid (GABA) has essential physiological functions in the human body. A novel method using glutamate decarboxylase (GAD) entrapped in polyvinyl alcohol (PVA)-sodium alginate (SA) capsules provides a green biological strategy for GABA synthesis. In this investigation, the stability range of immobilized GAD was effectively broadened, and immobilized GAD could be repeatedly used as a batch and fixed-bed column catalyst. The immobilized enzymes were stable and retained 89% of their activity in a pH range of 4.0-5.6, while there was an approximately 50% decrease in free GAD activity in the pH range of 4.8 ± 0.4. The immobilized GAD affinity to the substrate improved, and this was evidenced by the apparent decrease in Km to 13.3 mmol/L from the 30.9 mmol/L for free GAD. The immobilized GAD retained >90.6% activity after eight cycles and a near-100% enzyme activity retention after 120 h of a continuous fixed-bed column catalyst operation. This study has thus presented an effective PVA-SA-GAD immobilization method that could be used to continuously scale-up GABA biosynthesis.

Advances in 4-Hydroxyphenylacetate-3-hydroxylase Monooxygenase.

Catechols have important applications in the pharmaceutical, food, cosmetic, and functional material industries. 4-hydroxyphenylacetate-3-hydroxylase (4HPA3H), a two-component enzyme system comprising HpaB (monooxygenase) and HpaC (FAD oxidoreductase), demonstrates significant potential for catechol production because it can be easily expressed, is highly active, and exhibits ortho-hydroxylation activity toward a broad spectrum of phenol substrates. HpaB determines the ortho-hydroxylation efficiency and substrate spectrum of the enzyme; therefore, studying its structure-activity relationship, improving its properties, and developing a robust HpaB-conducting system are of significance and value; indeed, considerable efforts have been made in these areas in recent decades. Here, we review the classification, molecular structure, catalytic mechanism, primary efforts in protein engineering, and industrial applications of HpaB in catechol synthesis. Current trends in the further investigation of HpaB are also discussed.

Modification of the 4-Hydroxyphenylacetate-3-hydroxylase Substrate Pocket to Increase Activity towards Resveratrol.

4-Hydroxyphenylacetate-3-hydroxylase (4HPA3H; EC 1.14.14.9) is a heterodimeric flavin-dependent monooxygenase complex that catalyzes the ortho-hydroxylation of resveratrol to produce piceatannol. Piceatannol has various health benefits and valuable applications in food, medicine, and cosmetics. Enhancing the catalytic activity of 4HPA3H toward resveratrol has the potential to benefit piceatannol production. In this study, the critical amino acid residues in the substrate pocket of 4HPA3H that affect its activity toward resveratrol were identified using semi-rational engineering. Two key amino acid sites (I157 and A211) were discovered and the simultaneous "best" mutant I157L/A211D enabled catalytic efficiency (Kcat/Km-resveratrol) to increase by a factor of 4.7-fold. Molecular dynamics simulations indicated that the increased flexibility of the 4HPA3H substrate pocket has the potential to improve the catalytic activity of the enzyme toward resveratrol. On this basis, we produced 3.78 mM piceatannol by using the mutant I157L/A211D whole cells. In this study, we successfully developed a highly active 4HPA3H variant for the hydroxylation of resveratrol to piceatannol.

Superpixel-based sub-hologram method for real-time color three-dimensional holographic display with large size.

One of the biggest challenges for large size three-dimensional (3D) holographic display based on the computer-generated hologram (CGH) is the trade-off between computation time and reconstruction quality, which has limited real-time synthesis of high-quality holographic image. In this paper, we propose a superpixel-based sub-hologram (SBS) method to reduce the computation time without sacrificing the quality of the reconstructed image. The superpixel-based sub-hologram method divides the target scene into a collection of superpixels. The superpixels are composed of adjacent object points. The region of the superpixel-based sub-hologram corresponding to each superpixel is determined by an approximation method. Since the size and the complexity of the diffraction regions are reduced, the hologram generation time is decreased significantly. The computation time has found to be reduced by 94.89% compared with the conventional sub-hologram method. It is shown that the proposed method implemented on the graphics processing unit (GPU) framework can achieve real-time (> 24 fps) color three-dimensional holographic display with a display size of 155.52 mm × 276.48 mm.

Optimized computer-generated hologram for enhancing depth cue based on complex amplitude modulation.

In this Letter, we introduce a computer-generated hologram (CGH) optimization method to enhance the depth cue based on complex amplitude modulation (CAM). An iterative algorithm is designed to generate the optimized random phase (ORAP) according to the size of the target image and the bandwidth limitation condition. The ORAP with limited bandwidth is used as the initial phase of the target image and the hologram is encoded based on the analytical formula. Our proposal can maintain the advantages of CAM and achieve holographic three-dimensional (3D) display with an enhanced depth cue. It is expected that the proposed method could be widely used in holographic field in the future.

Color dynamic holographic display based on complex amplitude modulation with bandwidth constraint strategy.

In this Letter, we introduce a multiplexing encoding method with a bandwidth constraint strategy to realize a color dynamic holographic display based on complex amplitude modulation (CAM). The method first uses the angular spectrum method (ASM) with a bandwidth constraint strategy to calculate the diffracted wavefronts of red, green, and blue channels. Then the diffracted wavefronts of three channels are synthesized into a color-multiplexed hologram (CMH) based on the double-phase method after they interfere with off-axis reference lights. The color 3D objects can be reconstructed when the combination of red, green, and blue lights is used to illuminate the double-phase CMH, and a 4f system with a slit filter is introduced to extract the desired spectrums. Numerical simulations and optical experiments are performed to verify the effectiveness of the proposed method and the results show that it can achieve a color holographic display with high quality. Our proposal is simple and fast, and the display system is compact. It is expected that our proposed method could in future be widely used in the holographic field.

Anatomical Basis for Malar Augmentation Injection With the Zygomatic Ligamentous System.

BACKGROUND: The malar augmentation injection has gained popularity in recent years, but the exact location of each injection site has not been clearly identified. OBJECTIVE: To discover ideal injection sites by comprehensively considering the distributions of ligaments, muscles, and vessels. MATERIALS AND METHODS: Eighteen cadaver heads were dissected to investigate the zygomatic ligamentous system and to measure the position of muscles. Sixty-six cadaver heads were subjected to computed tomographic scanning and three-dimensional vessel reconstruction. Radiological evaluation of the fillers was performed before and after experimental injection in one hemiface and dissected to confirm safe delivery. Five patients were enrolled in a prospective clinical study. 2D and 3D photographs were taken before and after the injections for comparison. RESULTS: Site 1 was defined along the zygomatic arch, except the first 1/4 length and the midline of the arch. Site 2 was on the body of the zygoma, superior to the level of the infraorbital foramen and medial to the jugale. Site 3 was defined in the anteromedial midface approximately 30 mm below the lateral canthus. CONCLUSION: Injections at these 3 sites can be performed within the range of the ligaments to achieve effective lifting effects and minimize potential complications.

Reconstruction of the glutamate decarboxylase system in Lactococcus lactis for biosynthesis of food-grade γ-aminobutyric acid.

Gamma-aminobutyric acid (GABA), an important bioactive compound, is synthesized through the decarboxylation of L-glutamate (L-Glu) by glutamate decarboxylase (GAD). The use of lactic acid bacteria (LAB) as catalysts opens interesting avenues for the biosynthesis of food-grade GABA. However, a key obstacle involved in the improvement of GABA production is how to resolve the discrepancy of optimal pH between the intracellular GAD activity and cell growth. In this work, a potential GAD candidate (LpGadB) from Lactobacillus plantarum was heterologously expressed in Escherichia coli. Recombinant LpGadB existed as a homodimer under the native conditions with a molecular mass of 109.6 kDa and exhibited maximal activity at 40°C and pH 5.0. The Km value and catalytic efficiency (kcat/Km) of LpGadB for L-Glu was 21.33 mM and 1.19 mM-1s-1, respectively, with the specific activity of 26.67 µM/min/mg protein. Subsequently, four C-terminally truncated LpGadB mutants (GadBΔC10, GadBΔC11, GadBΔC12, GadBΔC13) were constructed based on homology modeling. Among them, the mutant GadBΔC11 with highest catalytic activity at near-neutral pH values was selected. In further, the GadBΔC11 and Glu/GABA antiporter (GadC) of Lactococcus lactis were co-overexpressed in the host L. lactis NZ3900. Finally, after 48 h of batch fermentation, the engineered strain L. lactis NZ3900/pNZ8149-gadBΔC11C yielded GABA concentration up to 33.52 g/L by applying a two-stage pH control strategy. Remarkably, this is the highest yield obtained to date for GABA from fermentation with L. lactis as a microbial cell factory.Key points• The GadB from L. plantarum was heterologously expressed in E. coli and biochemically characterized.• Deletion of the C-plug in GadB shifted its pH-dependent activity toward a higher pH.• Reconstructing the GAD system of L. lactis is an effective approach for improving its GABA production.

Three-Dimensional Computed Tomography Scanning of Temporal Vessels to Assess the Safety of Filler Injections.

BACKGROUND: Temple filler injection is one of the most common minimally invasive cosmetic procedures involving the face; however, vascular complications are not uncommon. OBJECTIVES: This study aimed to investigate the anatomy of the temporal vessels and provide a more accurate protocol for temple filler injection. METHODS: Computed tomography (CT) scans of 56 cadaveric heads injected with lead oxide were obtained. We then used Mimics software to construct 3-dimensional (3D) images of the temporal vessels described by a coordinate system based on the bilateral tragus and right lateral canthus. RESULTS: In the XOY plane, the superficial temporal artery (STA), middle temporal artery (MTA), zygomatico-orbital artery (ZOA), posterior branch of the deep temporal artery (PDTA), and lateral margin of the orbital rim divide the temple into 4 parts (A, B, C, and D). The probabilities of the STA, MTA, ZOA, and PDTA appearing in parts A, B, C, and D were 30.73%, 37.06%, 39.48%, and 77.18%, respectively. In 3D images, these vessels together compose an arterial network that is anastomosed with other vessels, such as the external carotid, facial, and ocular arteries. CONCLUSIONS: 3D CT images can digitally elucidate the exact positions of temporal vessels in a coordinate system, improving the safety of temple filler injections in a clinical setting.

Parallel Strategy Increases the Thermostability and Activity of Glutamate Decarboxylase.

Glutamate decarboxylase (GAD; EC 4.1.1.15) is a unique pyridoxal 5-phosphate (PLP)-dependent enzyme that specifically catalyzes the decarboxylation of L-glutamic acid to produce γ-aminobutyric acid (GABA), which exhibits several well-known physiological functions. However, glutamate decarboxylase from different sources has the common problem of poor thermostability that affects its application in industry. In this study, a parallel strategy comprising sequential analysis and free energy calculation was applied to identify critical amino acid sites affecting thermostability of GAD and select proper mutation contributing to improve structure rigidity of the enzyme. Two mutant enzymes, D203E and S325A, with higher thermostability were obtained, and their semi-inactivation temperature (T5015) values were 2.3 °C and 1.4 °C higher than the corresponding value of the wild-type enzyme (WT), respectively. Moreover, the mutant, S325A, exhibited enhanced activity compared to the wild type, with a 1.67-fold increase. The parallel strategy presented in this work proved to be an efficient tool for the reinforcement of protein thermostability.

A Single Mutation Increases the Thermostability and Activity of Aspergillus terreus Amine Transaminase.

Enhancing the thermostability of (R)-selective amine transaminases (AT-ATA) will expand its application in the asymmetric synthesis of chiral amines. In this study, mutual information and coevolution networks of ATAs were analyzed by the Mutual Information Server to Infer Coevolution (MISTIC). Subsequently, the amino acids most likely to influence the stability and function of the protein were investigated by alanine scanning and saturation mutagenesis. Four stabilized mutants (L118T, L118A, L118I, and L118V) were successfully obtained. The best mutant, L118T, exhibited an improved thermal stability with a 3.7-fold enhancement in its half-life (t1/2) at 40 °C and a 5.3 °C increase in T5010 compared to the values for the wild-type protein. By the differential scanning fluorimetry (DSF) analysis, the best mutant, L118T, showed a melting temperature (Tm) of 46.4 °C, which corresponded to a 5.0 °C increase relative to the wild-type AT-ATA (41.4 °C). Furthermore, the most stable mutant L118T displayed the highest catalytic efficiency among the four stabilized mutants.

Three-Dimensional Computed Tomographic Study on the Periorbital Branches of the Ophthalmic Artery: Arterial Variations and Clinical Relevance.

BACKGROUND: Filler injection is a popular cosmetic procedure, but it can entail vascular complications. Periorbital injections have the highest risk within the entire injection area. OBJECTIVES: The authors sought to systematically screen for periorbital arterial variations prior to treatment. METHODS: The external carotid arteries of 10 cadaveric heads were infused with adequate lead oxide contrast. The facial and superficial temporal arteries of another 11 cadaveric heads were injected with the contrast in sequential order. Computed tomography (CT) scanning was performed after injection of contrast, and 3-dimensional (3D) CT scans were reconstructed using validated algorithms. RESULTS: Three types of periorbital blood vessels were found to derive from the ophthalmic artery, including 30% directly originating from the ophthalmic artery, 65% originating from its trochlear branch, and 5% originating from its supraorbital branch. In the forehead, the ophthalmic artery, originating from the internal carotid arteries, formed anastomoses between the frontal branch of the superficial temporal artery, originating from the external carotid artery, with the deep and superficial branches of the supratrochlear and supraorbital arteries, respectively. The lateral orbit and malar plexus can be classified into 4 types based on the trunk artery: the zygomatic orbital artery (27%), the transverse facial artery (23%), the premasseteric branch of the facial artery (19%), and all 3 contributing equally (31%). CONCLUSIONS: Postmortem 3D CT can map periorbital arterial variations. The branching pattern of the ophthalmic artery, the ophthalmic angiosome in the forehead, and the distribution of the lateral orbit and malar plexus were identified at high resolution to guide clinical practice.

Lactobacillus brevis CGMCC 1306 glutamate decarboxylase: Crystal structure and functional analysis.

Glutamate decarboxylase (GAD), which is a unique pyridoxal 5-phosphate (PLP)-dependent enzyme, can catalyze α-decarboxylation of l-glutamate (L-Glu) to γ-aminobutyrate (GABA). The crystal structure of GAD in complex with PLP from Lactobacillus brevis CGMCC 1306 was successfully solved by molecular-replacement, and refined at 2.2 Šresolution to an Rwork factor of 18.76% (Rfree = 23.08%). The coenzyme pyridoxal 5-phosphate (PLP) forms a Schiff base with the active-site residue Lys279 by continuous electron density map, which is critical for catalysis by PLP-dependent decarboxylase. Gel filtration showed that the active (pH 4.8) and inactive (pH 7.0) forms of GAD are all dimer. The residues (Ser126, Ser127, Cys168, Ile211, Ser276, His278 and Ser321) play important roles in anchoring PLP cofactor inside the active site and supporting its catalytic reactivity. The mutant T215A around the putative substrate pocket displayed an 1.6-fold improvement in catalytic efficiency (kcat/Km) compared to the wild-type enzyme (1.227 mM-1 S-1 versus 0.777 mM-1 S-1), which was the highest activity among all variants tested. The flexible loop (Tyr308-Glu312), which is positioned near the substrate-binding site, is involved in the catalytic reaction, and the conserved residue Tyr308 plays a vital role in decarboxylation of L-Glu.

Exploring the contributions of two glutamate decarboxylase isozymes in Lactobacillus brevis to acid resistance and γ-aminobutyric acid production.

BACKGROUND: The glutamate decarboxylase (GAD) system of Lactobacillus brevis involves two isoforms of GAD, GadA and GadB, which catalyze the conversion of L-glutamate to γ-aminobutyric acid (GABA) in a proton-consuming reaction contributing to intracellular pH homeostasis. However, direct experimental evidence for detailed contributions of gad genes to acid tolerance and GABA production is lacking. RESULTS: Molecular analysis revealed that gadB is cotranscribed in tandem with upstream gadC, and that expression of gadCB is greatly upregulated in response to low ambient pH when cells enter the late exponential growth phase. In contrast, gadA is located away from the other gad genes, and its expression was consistently lower and not induced by mild acid treatment. Analysis of deletion mutations in the gad genes of L. brevis demonstrated a decrease in the level of GAD activity and a concomitant decrease in acid resistance in the order of wild-type> ΔgadA> ΔgadB> ΔgadC> ΔgadAB, indicating that the GAD activity mainly endowed by GadB rather than GadA is an indispensable step in the GadCB mediated acid resistance of this organism. Moreover, engineered strains with higher GAD activities were constructed by overexpressing key GAD system genes. With the proposed two-stage pH and temperature control fed-batch fermentation strategy, GABA production by the engineered strain L. brevis 9530: pNZ8148-gadBC continuously increased reaching a high level of 104.38 ± 3.47 g/L at 72 h. CONCLUSIONS: This is the first report of the detailed contribution of gad genes to acid tolerance and GABA production in L. brevis. Enhanced production of GABA by engineered L. brevis was achieved, and the resulting GABA level was one of the highest among lactic acid bacterial species grown in batch or fed-batch culture.

Correction to: An efficient biocatalytic synthesis of imidazole-4-acetic acid.

In the original publication of the article, the affiliations of authors Jun Huang, Changjiang Lv and Jiaqi Mei were misplaced. The correct information for author affiliations is provided in this correction.

An efficient biocatalytic synthesis of imidazole-4-acetic acid.

OBJECTIVE: To develop a new and efficient biocatalytic synthesis method of imidazole-4-acetic acid (IAA) from L-histidine (L-His). RESULTS: L-His was converted to imidazole-4-pyruvic acid (IPA) by an Escherichia coli whole-cell biocatalyst expressing membrane-bound L-amino acid deaminase (mL-AAD) from Proteus vulgaris firstly. The obtained IPA was subsequently decarboxylated to IAA under the action of H2O2. Under optimum conditions, 34.97 mM IAA can be produced from 50 mM L-His, with a yield of 69.9%. CONCLUSIONS: Compared to the traditional chemical synthesis, this biocatalytic method for IAA production is not only environmentally friendly, but also more cost effective, thus being promising for industrial IAA production.

Simultaneous multi-piston measurement method in segmented telescopes.

We propose a method to simultaneously detect the multi-piston between segments. The relation between the piston of any two segments and amplitude of the modulation transfer function (MTF) sidelobes (MTFnph) is derived. The piston can be retrieved by this relation after measuring the MTFnph. This method's capture range is the operating light's coherence length, the accuracy is 0.026λ (λ = 633 nm) RMS. The MTF model of a mask with sparse multi-subaperture configuration is established. The arrangement rules, to avoid the sidelobes overlapping, are obtained. The mask with a sparse 18 sub-aperture configuration is designed, which makes the MTF sidelobes distribution non-redundant.

Phasing piston error in segmented telescopes.

To achieve a diffraction-limited imaging, the piston errors between the segments of the segmented primary mirror telescope should be reduced to λ/40 RMS. We propose a method to detect the piston error by analyzing the intensity distribution on the image plane according to the Fourier optics principle, which can capture segments with the piston errors as large as the coherence length of the input light and reduce these to 0.026λ RMS (λ = 633nm). This method is adaptable to any segmented and deployable primary mirror telescope. Experiments have been carried out to validate the feasibility of the method.