Transfer Carrier Research Articles

PEI-PEG-Coated Mesoporous Silica Nanoparticles Enhance the Antitumor Activity of Tanshinone IIA and Serve as a Gene Transfer Vector.

Tanshinone IIA (TanIIA) and gene therapy both hold promising potentials in hepatocellular carcinoma (HCC) treatment. However, low solubility and poor bioavailability of TanIIA limit its clinical application. Similarly, gene therapy with GPC3-shRNA, a type of short hairpin RNAs (shRNAs) capable of silencing the glypican-3 (GPC3) expression, is seriously limited due to its susceptibility to nuclease degradation and high off-target effects. In the present study, polyethyleneimine (PEI)-polyethylene glycol (PEG)-coated mesoporous silica nanoparticles (MSN-PEG) were used as a drug carrier. By encapsulating TanIIA into MSN-PEG, we synthesized MSN-TanIIA-PEG nanoparticles and observed the involved characteristics. This was followed by exploration of antitumor activity on the HepG2 cell lines in vitro. Meanwhile, in order to construct GPC3-shRNA plasmids, a shRNA sequence targeting GPC3 was synthesized and cloned into the pSLenti-U6 vector. Accordingly, the performance of MSN-PEG as a gene transfer carrier for GPC3-shRNA gene therapy of HCC in vitro was evaluated, including transfection efficiency and DNA binding biological characteristics. The results indicated successful encapsulation of TanIIA in MSN-PEG, which had satisfactory efficacy, favorable dispersity, suitable particle size, and sustained release effect. The in vitro anti-HCC effects of nano-TanIIA were greatly improved, which outperformed free-TanIIA in terms of proliferation and invasion inhibition, as well as apoptosis induction of HCC cells. As expected, MSN-PEG possessed excellent gene delivery capacity with good binding, release, and protection from RNase digestion. Using MSN-PEG as a gene carrier, the plasmids were successfully transfected into HepG2 cells, and both the mRNA and protein expressions of GPC3 were significantly downregulated. It was thus concluded that a sustained release TanIIA delivery system for HCC treatment was synthesized and that MSN-PEG could also serve as a gene transfer carrier for gene therapy. More interestingly, MSN-PEG may be a potential delivery platform that combines TanIIA and GPC3-shRNA together to enhance their synergistic effect.

Performance Comparison of single‐slope solar still loaded with various nanofluids

AbstractNanofluids are great heat transfer carriers for collecting thermal energy in solar thermal applications. In the present study, a theoretical study of single‐slope solar still (passive type) has been carried out by incorporating CuO, Al2O3, Ag, Fe2O3, and SiC‐water nanofluids at different volume concentrations (0.02, 0.05, 0.08, 0.12, and 0.2). This analysis has been carried out with an optimum water depth of 0.02m as obtained from the experimental and theoretical studies. In order to validate the model, the experiments were conducted on solar still and then performance of still was compared. The analytical expression of the characteristic equation using Runga‐Kutta ODE, for passive single slope solar still was found to be in good agreement with experiments carried out in Patiala, India. The total deviation for both experimental and theoretical distillate output of a still for a day was found to be 12.24%. Daily production for Al2O3‐water‐based nanofluid was found to be (14.22%) higher than simple solar still without nanofluid, followed by CuO (10.82%), Ag (8.11%), Fe2O3 (7.63%) and SiC (7.61%).

Enhancing Photoelectrochemical Energy Storage by Large-Area CdS-Coated Nickel Nanoantenna Arrays

The integration of thin films made up of periodic plasmonic nanostructures and semiconductors holds great potential to develop efficient technologies for photoelectrochemical solar energy conversion and storage. However, to date, only periodic nanoantenna arrays made up of Au have been explored, posing severe limitations in terms of scalability and costs. Here, we show that nickel nanopillar arrays can support complex electromagnetic resonances that strongly enhance the photoelectrochemical response of CdS thin films. By controlling the pitch size and diameter of the nanopillars, we obtain broadband light absorption from the ultraviolet (UV) to the near-infrared (NIR) wavelength range, thus achieving large photocurrent enhancements compared to a planar Ni/CdS sample and in line with those generated by previously reported Au nanostructures. The photocurrent enhancement is attributed to photonic modes in the UV and hybrid cavity-plasmonic modes in the visible and NIR ranges, which give rise to efficient energy transfer and hot carrier injection between metallic structures, the semiconductor, and the electrolyte. The developed nanopillar arrays are promising candidates for photoelectrochemical devices fully exploiting the solar spectrum and using Earth-abundant raw materials.

Sc2CF2/Janus MoSSe heterostructure: A potential Z-scheme photocatalyst with ultra-high solar-to-hydrogen efficiency

Aroused by plant photosynthesis, Z-scheme heterostructures have been considered as a potential photocatalyst for solar-driven water splitting to solve the current energy crisis. Hence, based on first-principles calculations, we predict that Sc2CF2/Janus MoSSe can be used as a Z-scheme heterostructure for efficient photocatalytic water splitting. The research shows that the traditional type-II to direct Z-scheme heterostructure conversion can be realized through different stacking methods of Sc2CF2 and Janus MoSSe. Through the built-in electric field and band bending theory, the transition path of photogenerated carriers is analyzed, which reveals the completely different photocatalytic mechanism of type-II and direct Z-scheme heterostructure. Surprisingly, the direct Z-scheme heterostructure displays a high overpotential of the hydrogen evolution reaction (χH2=1.01 eV) and the oxygen evolution reaction (χO2=1.46 eV) compared with the type II heterostructure. More importantly, the direct Z-scheme heterostructure has an ultra-high solar-to-hydrogen (STH) efficiency (36.1%), which breaks through the limitation of traditional theoretical efficiency and reveals a tremendous prospect of commercial application. Furthermore, the calculation of free energy confirms that the water splitting reaction on the direct Z-scheme heterostructure occur spontaneously under the external potential, but not for type-II heterostructure. Finally, introducing the additional electronic conductor (N-doped graphene) can accelerate the electron (hole) transfer and interlayer carrier recombination, which will further improve the photocatalytic performance of Z-scheme heterostructure. These distinctive features make Sc2CF2/Janus MoSSe heterostructure as promising Z-scheme photocatalyst for water splitting.

Enhanced solar water splitting using plasmon-induced resonance energy transfer and unidirectional charge carrier transport.

Solar water splitting by photoelectrochemical (PEC) reactions is promising for hydrogen production. The gold nanoparticles (AuNPs) are often applied to promote the visible response of wideband photocatalysts. However, in a typical TiO2/AuNPs structure, the opposite transfer direction of excited electrons between AuNPs and TiO2 under visible light and UV light severely limits the solar PEC performance. Here we present a unique Pt/TiO2/Cu2O/NiO/AuNPs photocathode, in which the NiO hole transport layer (HTL) is inserted between AuNPs and Cu2O to achieve unidirectional transport of charge carriers and prominent plasmon-induced resonance energy transfer (PIRET) between AuNPs and Cu2O. The measured applied bias photon-to-current efficiency and the hydrogen production rate under AM 1.5G illumination can reach 1.5% and 16.4 μmol·cm-2·h-1, respectively. This work is original in using the NiO film as the PIRET spacer and provides a promising photoelectrode for energy-efficient solar water splitting.

Green and efficient photodegradation of norfloxacin with CsPbBr3-rGO/Bi2WO6 S-scheme heterojunction photocatalyst

Modern chemistry aims to identify excellent photocatalyst for pollution challenge associated with the antibiotics-containing wastewater. In this contribution, a novel CsPbBr3-rGO/Bi2WO6 S-scheme heterojunction with superior stability and excellent photocatalytic activity was achieved via trimercaptopropionic acid (MPA) modification for norfloxacin photodegradation. Here, MPA acted not only as an organic ligand to stable the composite by formation of strong -SH-Pb- bond and -COO-Bi-O- bond, but also worked as an electronic bridge to transfer and separate photogenerated carriers. The CsPbBr3-rGO/Bi2WO6 composite displayed the excellent photocatalytic activity compare with pure Bi2WO6 and rGO/Bi2WO6, and the norfloxacin degradation rate was about 66.79% with 120 min under visible light irradiation. The results of the UV-Vis diffuse reflectance spectra, PL spectra, transient photocurrent response, and reactive-species-trapping experiments indicated that the expanding light-harvesting scope, efficient charge separation ability, and large amounts of active species, are the major reasons for the enhancement photocatalytic activity of CsPbBr3-rGO/Bi2WO6 composite. According to the cycle experiment, the photodegradation rate of norfloxacin is no significant decrease, the XRD pattern and FTIR spectra before and after norfloxacin degradation displayed almost no change, indicating the superior stability of the CsPbBr3-rGO/Bi2WO6 composite. This work not only provides a new opportunity to strengthen the stability and charger-transfer efficiency of CsPbBr3 nanocrystals (NCs), but also opens up a new insight for photocatalytic application of CsPbBr3 NCs.

Improving the Modulation Bandwidth of GaN‐Based Light‐Emitting Diodes for High‐Speed Visible Light Communication: Countermeasures and Challenges

Visible light communication (VLC) has attracted widespread attention for wireless communications. The popularity of GaN‐based light‐emitting diodes (LEDs) has also laid a solid foundation for the application of VLC. As the light source of VLC, LED's modulation bandwidth directly determines the speed of communication. Herein, reviewing progress on modulation bandwidth improvement schemes of GaN LEDs transmitter is reviewed, covering aspects from epitaxial to devices. Epitaxial approaches include c‐polar facet epitaxial optimization, non/semipolar facet epitaxial growth, and chip scheme such as micro‐LEDs, nano‐LEDs, resonant cavity‐LEDs (RC‐LEDs), plasmon, and metacavity LEDs. In terms of white LEDs, approaches to tackle the slow Stokes transfer and long carrier life for conventional phosphors including new color‐conversion materials (CCMs) and new energy transfer routes are reviewed. This review promotes the development of GaN‐based LEDs as the transmitter for high‐speed VLC.

Excellent catalytic activity of two-dimensional Ti2C and Ti2CT2 (T = O, F, OH) monolayers on hydrogen storage of MgH2: First-principles calculations

Two-dimensional Ti2C MXene has been recognized as an effective additive to improve the dehydrogenation of light metal hydride. Here, an MgH2 molecule adsorption on 2D Ti2C and Ti2CT2 monolayers were theoretically studied. Adsorption energy, the charge transfer and the electronic density of states were investigated via first-principles calculations based on density functional theory (DFT). We found that adopting bare Ti2C and functionalized Ti2CT2 to adsorb MgH2 molecule is not a good strategy. The charge transfer and DOS results revealed that bare Ti2C monolayer can enhance the dehydrogenation of MgH2 more effectively than functionalized Ti2CT2. Moreover, we have explored the catalytic mechanism of 2D Ti2C MXene on MgH2 using ab initio molecular dynamic (ab-init MD) simulations of MgH2/Ti2C heterostructure interface. It is found that the formation of TiH2 in Ti2C/MgH2 interface serves as a catalyst during the dehydrogenation of MgH2. Based on the analyses of electronic structure and the results of ab-init MD dynamic simulations, we found that the catalytic effects of 2D Ti2C MXene on MgH2 are presented in two aspects: as the electron e− transfer carrier and in-situ formed catalyst TiH2, they work together to enhance the dehydrogenation performance of MgH2.

Response to Bombyx mori nucleopolyhedrovirus infection in silkworm: Gut metabolites and microbiota

The diversity of microbiota and metabolites in the digestive tract gut is important in physiology and homeostasis, nutrient uptake and virus infection. In lepidopteran insect model silkworms, little is known about how microbiota and metabolites are altered after oral infection with BmNPV. Herein, we used 16S rDNA sequencing and metabolomics to show that the gut microbiota and metabolites of silkworm midgut are significantly altered after BmNPV infection. Kyoto Encyclopedia of Genes and Genomes analysis revealed enrichment of flavone and flavonol biosynthesis, glycosyltransferases, and electron transfer carriers signaling pathways, suggesting potential roles in viral infection. Infection also changed the abundance of metabolites in the digestive tract gut, where most pathways were related to metabolism of amino acids, fatty acids and other pathways (e.g., citrate cycle). In addition, a correlation was observed between digestive tract gut microbiota and metabolites. These results shed light on the interaction between digestive tract gut microbiota, metabolites and host-virus interaction, and enhance our understanding of viral infection links to midgut microbiota and metabolic activity in the silkworm.

Photocatalytic self-cleaning properties of m-phenylene isophthalamide membranes enhanced by immobilization of GO-ZnO-Ag for dye wastewater disposal

Drawing self-cleaning technology into polymer membranes offers an extensive solution to overcome the membrane fouling obstacle. Herein, the GO-ZnO-Ag nano-hybrid particles with photocatalytic activity prepared via the microwave hydrothermal method were immobilized in poly(m-phenylene isophthalamide) (PMIA) membranes. Not only was the thorny issue in catalyst recovery avoided, but also the satisfactory photocatalytic self-cleaning performance of the polymer membrane was awarded. GO and noble metal silver nanoparticles (AgNPs) acted as a conductive electron transfer carrier and an electron host, respectively, which hindered the recombination rate of excited electrons and holes on ZnO under UV light. The UV-driven PMIA membrane photodegradation rates of MB and Cr(VI) were up to 97.2% and 94.3%, respectively, at 150 min on photodegradation kinetics. Also, MB was completely degraded at 180 min. For MB and Cr(VI) mix solutions, their degradation efficiencies were 78.1% and 71%, respectively. The BSA rejection rate of the modified polymer membrane was 93.8%, and the water flux was 408.8 (L·m−2·h−1). Permeability was maintained at a high level after repeated use. Therefore, the newly designed PMIA/GO-ZnO-Ag series membranes could expand the application of polymers in wastewater disposal industry.

Enhanced Charge Separation in Ternary Bulk-Heterojunction Organic Solar Cells by Fullerenes.

Carrier generation dynamics in binary PTB7-Th:COi8DFIC (1:1.5) and ternary PTB7-Th:COi8DFIC:PC71BM (1:1.05:0.45) composites were investigated to identify the origins of high power conversion efficiencies (PCEs) in ternary bulk-heterojunction (BHJ) organic solar cells. Steady-state photoluminescence and time-resolved photoinduced absorption spectroscopic analyses revealed that the ternary composite exhibited faster hole transfer from COi8DFIC to PTB7-Th (8 ps compared to 21 ps in the binary composite), which led to an improved exciton separation yield in COi8DFIC (94% compared to 68% in the binary composite). Improved intermixing of the component materials and efficient electron transfer from COi8DFIC to PC71BM facilitated enhancement in the hole transfer rate. The COi8DFIC-to-PC71BM electron transfer promoted an electron transport cascade over PTB7-Th, COi8DFIC, and PC71BM, which efficiently deactivated back-electron transfer (carrier recombination loss) from COi8DFIC to PTB7-Th at ∼160 ps and assisted in improving the PCE of the ternary BHJ cell (13.4% compared to 10.5% in the binary BHJ cell).

Development of an H2S emission model for wastewater treatment plants

ABSTRACT Modeling and prediction of H2S emission from wastewater are important since gaseous H2S will induce significant corrosion and odor problems. Most previous studies focused on H2S emission of wastewater in pipeline systems, which may not be fit for H2S emission in wastewater treatment plants (WWTPs). This study provided a two-phase mass transfer model for prediction of H2S emission concentrations. The model is based on the mass transfer rate equation of the mass transfer impetus, expressed by the concentration difference. The main parameters of the model are the mass transfer coefficient, the carrier gas flow rate and the concentration of H2S in liquid phase. The results showed that the model can simulate and predict H2S emission concentrations of various processes in WWTPs. Moreover, the model can analyze and predict the influences of different pH values, mass transfer coefficients and carrier gas flow rates on H2S emission concentrations and loads. Therefore, the model provides theoretical guidance for design of WWTPs regarding H2S emissions. Implications: Modeling and prediction of H2S emission from wastewater are quite important since gaseous H2S will induce significant corrosion and odor problems. Most of previous studies are focused on H2S emission from wastewater in pipeline system, which may not be fit for H2S emission in wastewater treatment plants (WWTPs). Thus in this study, a model for predicting H2S emission from typical units of WWTPs is established and verified. Moreover, the influences of pH values, mass transfer coefficients and carrier gas flow rates on H2S emission are analyzed. The model can be a useful tool to predict the H2S concentration in odor gas collection system of WWTP and understand the behaviors of H2S emission under different WWTPs operating conditions.

"I've never been at the crime scene!" - gloves as carriers for secondary DNA transfer.

Over recent years, DNA profiling techniques have become highly sensitive. Even small amounts of DNA at crime scenes can be analysed leading to new defence strategies. At court, defence lawyers rarely question the existence of a DNA trace (source level) but challenge how the DNA was transferred to the scene (activity level). Nowadays, the most common defence strategy is to claim that somebody else had stolen the defendant's gloves and used them while breaking and entering. In this study we tested this statement. Using gloves made of different material (cloth, leather, rubber) and varying secondary transfer surfaces (wood, metal, glass), we simulated a few of the most likely transfer scenarios that occur during breaking and entering. While we detected the presence of DNA on the outside of 92 of the 98 gloves tested, we observed only one case of secondary transfer in a total of 81 transfer experiments. This data demonstrates that secondary transfer under conditions resembling realistic conditions is a very rare event.

Responses of root exudates to intercropping of Chinese milk vetch with rape.

Root exudates are important carriers for material exchange and information transfer between plant and soil, and important regulators of crop-soil-microorganism interaction in intercropping systems. We examined the interaction between crops in intercropping system by setting three treatments, monoculture Chinese milk vetch, monoculture rape and Chinese milk vetch intercropped with rape. The responses of root exudates were emphatically analyzed. The results showed that 391 root exudates were detected, with 93 of which being identified and divided into nine types of metabo-lites. Among them, organooxygen compounds were the most abundant, mainly in the form of ribitol. Under different planting patterns, root exudates of Chinese milk vetch and rape were significantly different. The characteristics of root exudates in intercropping were similar to monoculture rape, but significantly different from monoculture Chinese milk vetch. Among the root exudates in different planting modes, only 9-fluorenone 1 was negatively correlated with others. The differential root exudates were mainly benzenoids, lipids and lipid-like molecules, organic acids and derivatives, and organooxygen compounds. The benzenoids, lipids and lipid-like molecules were important types that characterized the changes of root exudates of Chinese milk vetch and rape. Chinese milk vetch intercropping with rape changed the characteristics of root exudates, which were closely related to benzenoids, lipids, and lipid-like molecules.

Salt-air template synthesis of Na and O doped porous graphitic carbon nitride nanorods with exceptional photocatalytic H2 evolution activity

Photocatalyst fabrication process plays the central role in photocatalytic hydrogen (H2) evolution reaction. Herein, we synthesize Na+ functionalized porous graphitic carbon nitride nanorods (Na-CNNR) via a facile one-pot calcination method. The morphology and size of Na-CNNR are controllable by changing the amount of sodium salt; both sodium salt and air are essential to the unique structure and oxygen doping. The obtained Na-CNNR contains abundant oxygen in the graphitic carbon nitride (CN) plane. The optimized Na20-CNNR (20 wt% Na2S2O3•5H2O to dicyanamide) photocatalyst exhibits a high surface area with enhanced visible light absorption. Besides, Na20-CNNR displays fast charge transfer and high carrier separation rate characterized by photoluminescence (PL) spectroscopy and electrochemical test. Through time-resolved transient absorption spectra analysis, the trapped unreactive electron accumulation can be highly restrained, favoring efficient active electron de-trapping and transfer. The optimized Na20-CNNR sample exhibits the highest photocatalytic H2 evolution rate of 7.46 mmol/h/g under visible light irradiation (>400 nm, 100 mW/cm2), which is up to 85 times that of the bare CN and 27 times that of Na+ doped graphitic carbon nitride nanoparticles (Na20–CNNP). Meanwhile, the cyclability tests indicate that Na20-CNNR displays robust stability over 24 h.

Fabrication of polymer electrolyte via lithium salt-induced surface-initiated radical polymerization for lithium metal batteries

The fabrication of flexible polymer electrolytes (PEs) which possess simultaneously high thermal stability, robust mechanical strength, and high ionic conductivity is very challenging for lithium (Li) batteries. Herein, cellulose-based PE is fabricated via a Li salt-induced surface-initiated radical polymerization of polyethylene glycol methyl ether acrylate (PEGA). The polymerization of PEGA is catalyzed by various Li salts, such as Li perchlorate (LiClO4), bis(trifluoromethane)sulfonimide Li (LiTFSI), Li difluoro(oxalato)borate (LiDFOB), and LiClO4/LiDFOB, which also serve as charge transfer carriers in PEs. The Li salt can be used as the catalyst to promote the cleavage of C–Br bond on the surface of Br-modified cellulose, and then initiate the polymerization of PEGA. The PE obtained from the dual salt (LiClO4/LiDFOB)-induced radical polymerization system exhibits high ionic conductivity of 3.5 × 10−5 S cm−1 at 30 °C, good thermal stability (up to 240 °C), and wide electrochemical stability window (5.0 V vs. Li/Li+). Moreover, Li/PE/Li symmetric cells show good interfacial stability between PE and Li foil and the assembled Li/PE/LiFePO4 cells possess 150 mA h g−1 at 0.1C. Li salt-induced surface-initiated polymerization provides a simple and efficient method for fabricating PE for high-performance Li metal batteries (LMBs).

Electron-Ion Coupling Mechanism to Construct Stable Output Performance Nanogenerator.

Recently, triboelectric nanogenerators (TENGs) have been promoted as an effective technique for ambient energy harvesting, given their large power density and high energy conversion efficiency. However, traditional TENGs based on the combination of triboelectrification effect and electrostatic induction have proven susceptible to environmental influence, which intensively restricts their application range. Herein, a new coupling mechanism based on electrostatic induction and ion conduction is proposed to construct flexible stable output performance TENGs (SOP-TENGs). The calcium chloride doped-cellulose nanofibril (CaCl2-CNF) film made of natural carrots was successfully introduced to realize this coupling, resulting from its intrinsic properties as natural nanofibril hydrogel serving as both triboelectric layer and electrode. The coupling of two conductive mechanisms of SOP-TENG was comprehensively investigated through electrical measurements, including the effects of moisture content, relative humidity, and electrode size. In contrast to the conventional hydrogel ionotronic TENGs that require moisture as the carrier for ion transfer and use a hydrogel layer as the electrode, the use of a CaCl2-CNF film (i.e., ion-doped natural hydrogel layer) as a friction layer in the proposed SOP-TENG effectively realizes a superstable electrical output under varying moisture contents and relative humidity due to the compound transfer mechanism of ions and electrons. This new working principle based on the coupling of electrostatic induction and ion conduction opens a wider range of applications for the hydrogel ionotronic TENGs, as the superstable electrical output enables them to be more widely applied in various complex environments to supply energy for low-power electronic devices.

Charge transfer states and carrier generation in 1D organolead iodide semiconductors

Naphthalene diimide based diammonium cations can be utilized to produce 1D organic/inorganic metal halide semiconductors with internal charge separation via charge transfer states that lie energetically below the metal-halide excitonic absorption.

Salt Tolerance Potential in Orchid Oncidium hybridum Plants Revealed by Halophenotyping and Genotyping

Orchid plants are thought to be glycophytes. Oncidium hybridum var. Gower Ramsey (OhGR) plants were tested for the halotolerance by cultivation in 0-5000mM NaCl solutions. Phenotypes such as leaf morphology and electrical conductivity of the salt treated plants for a week, and gene expression spectrums of different parts of those plants were analyzed. Electron transfer carrier genes OhFNR and OhFD as an example of house-keeping genes, a transcription factor OhMYB1R1and a phospholipase D gene OhPLDζ1 as tolerance responsive genes, were investigated with qPCR. It was found that OhGR plants absorbed salt without secretion, the leaves turned yellow in the salt treatment with a basal to upper manner and the electrical conductivity of the leave tissues increased accordingly with the leaf morphological change. The genes assessed showed stress timing and tissue specific differential spectrums in which OhFD-OhFNR were co-inhibited by salt stress, OhMYB1R1 and OhPLDs were stress inducible and enhanced. At the meanwhile, the upper leaves, the pseudobulbs and the roots kept morphologically normal and alive in most tested OhGR plants in various salt conditions tested, even a high amount of salt had been accumulated in the plants as revealed by electroconductivity measures. Our results show that OhGR plants have high salt tolerance potential based on their ordered cell and molecular mechanisms.

Recent Progress in Structural Studies on the GT-C Superfamily of Protein Glycosyltransferases.

Protein glycosylation is an essential covalent modification involved in protein secretion, stability, binding, folding, and activity. One or more sugars may be O-, N-, S-, or C-linked to specific amino acids by glycosyltransferases, which catalyze the transfer of these sugars from a phosphate-containing carrier molecule. Most glycosyltransferases are members of the GT-A, GT-B, or GT-C structural superfamilies. GT-C enzymes are integral membrane proteins that utilize a phospho-isoprenoid carrier for sugar transfer. To-date, two families of GT-Cs involved in protein glycosylation have been structurally characterized: the family represented by PglB, AglB, and Stt3, which catalyzes oligosaccharide transfer to Asn, and the family represented by Pmt1 and Pmt2, which catalyzes mannose transfer to Thr or Ser. This chapter reviews progress made over recent years on the structure and function of these two GT-C families.