Threonine functionalized colloidal cadmium sulfide (CdS) quantum dots: The role of solvent and counterion in ligand induced chiroptical properties.

The functionalization of semiconductor nanocrystals, quantum dots (QDs), with small organic molecules has been studied extensively to gain better knowledge on how to tune the electronic, optical and chiroptical properties of QDs. Chiral QDs have progressively emerged as key materials in a vast range of applications including biosensing and biorecognition, imaging, asymmetric catalysis, optoelectronic devices, and spintronics. To engage the full potential of the unique properties of chiral nanomaterials and be able to prepare them with tailorable chiroptical characteristics, it is essential to understand how chirality is rendered from chiral molecular ligands at the surface of nanocrystals to the electronic states of QDs. Using a series of polar protic and aprotic solvents together with ammonium (NH4+), tetramethylammonium (TMA+), and tetrabutylammonium (TBA+) countercations in the preparation of threonine-functionalized cadmium sulfide (Thr-CdS) QDs by phase transfer ligand exchange approach, we demonstrated the significance of the role both the solvent and the countercations play in the transfer of chirality from chiral molecular ligand to achiral semiconductor QDs as apparent by the modulations of the signatures and anisotropy of the circular dichroism (CD) spectra. Moreover, we have utilized tetrabutylammonium countercation to successfully synthesize chiral QDs in nonpolar cyclohexane solvent for the first time. This study provides further insights into the origin of the ligand induced chirality of colloidal nanomaterials and facilitates the synthesis of tailormade chiral QDs.

Minimally invasive adrenalectomy ­ Operative and perioperative results of transperitoneal and retroperitoneal adrenalectomies performed at the University of Szeged Department of Surgery during 23 years / Minimálisan invazív adrenalectomia - 23 év alatt végzett transperitonealis és retroperitonealis adrenalectomiák operatív és perioperatív eredményei a Szegedi Tudományegyetem Sebészeti Klinikán

Aim. Our goal was to evaluate operative and perioperative data of retroperitoneal (RP) and transperitoneal (TP) adrenalectomies performed at the University of Szeged Department of Surgery. Patients and method. During a retrospective cohort study including 174 adrenalectomies (28 RP; 146 TP) performed between 1998 and 2021, the following parameters were evaluated: rate of previous abdominal surgeries, conversion rate, operative time, intraoperative blood loss, tumor size, histology, hospital stay, early and late complications. Results. With significantly higher rate of previous abdominal surgeries [TP vs RP: 68 (46.57%) vs 4 (14%) P = 0.0021], there was no markable difference in conversion rate [TP vs RP: 7 (4.79%) vs 5 (18%), P = 0.312]. Significantly larger tumours were removed with TP (TP vs RP: 58.05 vs 34.8 mm, P = 0.016), with no markable difference in intraoperative blood loss (TP vs RP: 67.85 vs 50.2 ml, P = 0.157). Operative time was significantly shorter in TP (TP vs RP: 86.3 vs 134.5 min; P = 0.024). The most frequent histology was adenoma (TP vs RP: n = 95; 65.06% vs 64.3%). Pheochromocytoma occurred in 11 (7.53%) and 5 (17.8%) cases in TP and RP, respectively. We found no significant difference in hospital stay (TP vs RP: 5.125 vs 4.61 day; P = 0.413). Five- and 2 cases of early complications were seen in TP (splenic injury, postoperative fever, severe intraoperative bleeding, severe hypokalemia, surgical site infection) and RP (2 severe intraoperative bleeding), respectively. One lethal case of ventricular fibrillation and one delayed complication (postoperative abdominal wall hernia) were observed in TP. Conclusions. Both TP and RP are safe and simply reproducible minimally invasive techniques. According to our observation, RP adrenalectomy seems to be reserved for smaller lesions, while TP proves to be successful in removing enlarged and also malignant lesions with significantly shorter operative time.

Molecular interactions and inhibition of the SARS-CoV-2 main protease by a thiadiazolidinone derivative.

We report molecular interactions and inhibition of the main protease (MPro ) of SARS-CoV-2, a key enzyme involved in the viral life cycle. By using a thiadiazolidinone (TDZD) derivative as a chemical probe, we explore the conformational dynamics of MPro via docking protocols and molecular dynamics simulations in all-atom detail. We reveal the local and global dynamics of MPro in the presence of this inhibitor and confirm the inhibition of the enzyme with an IC50 value of 1.39 ± 0.22 µM, which is comparable to other known inhibitors of this enzyme.

Intracellular and Extracellular Antifreeze Protein Significantly Improves Mammalian Cell Cryopreservation.

Cell cryopreservation is an essential part of the biotechnology, food, and health care industries. There is a need to develop more effective, less toxic cryoprotective agents (CPAs) and methods, especially for mammalian cells. We investigated the impact of an insect antifreeze protein from Anatolica polita (ApAFP752) on mammalian cell cryopreservation using the human embryonic kidney cell line HEK 293T. An enhanced green fluorescent protein (EGFP)-tagged antifreeze protein, EGFP-ApAFP752, was transfected into the cells and the GFP was used to determine the efficiency of transfection. AFP was assessed for its cryoprotective effects intra- and extracellularly and both simultaneously at different concentrations with and without dimethyl sulfoxide (DMSO) at different concentrations. Comparisons were made to DMSO or medium alone. Cells were cryopreserved at -196 °C for ≥4 weeks. Upon thawing, cellular viability was determined using trypan blue, cellular damage was assessed by lactate dehydrogenase (LDH) assay, and cellular metabolism was measured using a metabolic activity assay (MTS). The use of this AFP significantly improved cryopreserved cell survival when used with DMSO intracellularly. Extracellular AFP also significantly improved cell survival when included in the DMSO freezing medium. Intra- and extracellular AFP used together demonstrated the most significantly increased cryoprotection compared to DMSO alone. These findings present a potential method to improve the viability of cryopreserved mammalian cells.

An insect antifreeze protein from Anatolica polita enhances the cryoprotection of Xenopus laevis eggs and embryos.

Cryoprotection is of interest in many fields of research, necessitating a greater understanding of different cryoprotective agents. Antifreeze proteins have been identified that have the ability to confer cryoprotection in certain organisms. Antifreeze proteins are an evolutionary adaptation that contributes to the freeze resistance of certain fish, insects, bacteria and plants. These proteins adsorb to an ice crystal's surface and restrict its growth within a certain temperature range. We investigated the ability of an antifreeze protein from the desert beetle Anatolica polita, ApAFP752, to confer cryoprotection in the frog Xenopus laevis. Xenopus laevis eggs and embryos microinjected with ApAFP752 exhibited reduced damage and increased survival after a freeze-thaw cycle in a concentration-dependent manner. We also demonstrate that ApAFP752 localizes to the plasma membrane in eggs and embryonic blastomeres and is not toxic for early development. These studies show the potential of an insect antifreeze protein to confer cryoprotection in amphibian eggs and embryos.

Apple juice and red wine induced mirror-image circular dichroism in quantum dots.

Juices, wines, and extracts from plants contain high concentrations of various chiral compounds such as carboxylic acids or sugars. Several prior studies reported the synthesis of metallic and semiconducting nanoparticles relying on components of complex biological solutions. Herein, we present preparation of chiral CdS and CdSe quantum dots (QDs) using apple juice and red wine via phase transfer ligand exchange. Although both apple juice and red wine contain a complex mixture of chiral and achiral compounds, we have successfully used them for selective induction of predicted chiroptical properties and confirmed L-malic acid from the apple juice and L-tartaric acid from the red wine as the chiral inducers. This work illustrates the capability of using complex mixtures to construct chiral QDs with desired chiroptical properties as well as potential of QDs to selectively report a chiral molecule in a complex chiral mixture without the need for elaborate chiral recognition system.

Intrinsically Disordered Bacterial Polar Organizing Protein Z, PopZ, Interacts with Protein Binding Partners Through an N-terminal Molecular Recognition Feature.

The polar organizing protein Z (PopZ) is necessary for the formation of three-dimensional microdomains at the cell poles in Caulobacter crescentus, where it functions as a hub protein that recruits multiple regulatory proteins from the cytoplasm. Although a large portion of the protein is predicted to be natively unstructured, in reconstituted systems PopZ can self-assemble into a macromolecular scaffold that directly binds to at least ten different proteins. Here we report the solution NMR structure of PopZΔ134-177, a truncated form of PopZ that does not self-assemble but retains the ability to interact with heterologous proteins. We show that the unbound form of PopZΔ134-177 is unstructured in solution, with the exception of a small amphipathic α-helix in residues M10-I17, which is included within a highly conserved region near the N-terminal. In applying NMR techniques to map the interactions between PopZΔ134-177 and one of its binding partners, RcdA, we find evidence that the α-helix and adjoining amino acids extending to position E23 serve as the core of the binding motif. Consistent with this, a point mutation at position I17 severely compromises binding. Our results show that a partially structured Molecular Recognition Feature (MoRF) within an intrinsically disordered domain of PopZ contributes to the assembly of polar microdomains, revealing a structural basis for complex network assembly in Alphaproteobacteria that is analogous to those formed by intrinsically disordered hub proteins in other kingdoms.

Structural Analysis of the Regulatory GAF Domains of cGMP Phosphodiesterase Elucidates the Allosteric Communication Pathway.

Regulation of photoreceptor phosphodiesterase (PDE6) activity is responsible for the speed, sensitivity, and recovery of the photoresponse during visual signaling in vertebrate photoreceptor cells. It is hypothesized that physiological differences in the light responsiveness of rods and cones may result in part from differences in the structure and regulation of the distinct isoforms of rod and cone PDE6. Although rod and cone PDE6 catalytic subunits share a similar domain organization consisting of tandem GAF domains (GAFa and GAFb) and a catalytic domain, cone PDE6 is a homodimer whereas rod PDE6 consists of two homologous catalytic subunits. Here we provide the x-ray crystal structure of cone GAFab regulatory domain solved at 3.3 Šresolution, in conjunction with chemical cross-linking and mass spectrometric analysis of conformational changes to GAFab induced upon binding of cGMP and the PDE6 inhibitory γ-subunit (Pγ). Ligand-induced changes in cross-linked residues implicate multiple conformational changes in the GAFa and GAFb domains in forming an allosteric communication network. Molecular dynamics simulations of cone GAFab revealed differences in conformational dynamics of the two subunits forming the homodimer and allosteric perturbations on cGMP binding. Cross-linking of Pγ to GAFab in conjunction with solution NMR spectroscopy of isotopically labeled Pγ identified the central polycationic region of Pγ interacting with the GAFb domain. These results provide a mechanistic basis for developing allosteric activators of PDE6 with therapeutic implications for halting the progression of several retinal degenerative diseases.

Changes in Cryopreserved Cell Nuclei Serve as Indicators of Processes during Freezing and Thawing.

The mechanisms underlying cell protection from cryoinjury are not yet fully understood. Recent biological studies have addressed cryopreserved cell survival but have not correlated the cryoprotection effectiveness with the impact of cryoprotectants on the most important cell structure, the nucleus, and the freeze/thaw process. We identified changes of cell nuclei states caused by different types of cryoprotectants and associate them with alterations of the freeze/thaw process in cells. Namely, we investigated both higher-order chromatin structure and nuclear envelope integrity as possible markers of freezing and thawing processes. Moreover, we analyzed in detail the relationship between nuclear envelope integrity, chromatin condensation, freeze/thaw processes in cells, and cryopreservation efficiency for dimethyl sulfoxide, glycerol, trehalose, and antifreeze protein. Our interdisciplinary study reveals how changes in cell nuclei induced by cryoprotectants affect the ability of cells to withstand freezing and thawing and how nuclei changes correlate with processes during freezing and thawing. Our results contribute to the deeper fundamental understanding of the freezing processes, notably in the cell nucleus, which will expand the applications and lead to the rational design of cryoprotective materials and protocols.

Chromatin architecture changes and DNA replication fork collapse are critical features in cryopreserved cells that are differentially controlled by cryoprotectants.

In this work, we shed new light on the highly debated issue of chromatin fragmentation in cryopreserved cells. Moreover, for the first time, we describe replicating cell-specific DNA damage and higher-order chromatin alterations after freezing and thawing. We identified DNA structural changes associated with the freeze-thaw process and correlated them with the viability of frozen and thawed cells. We simultaneously evaluated DNA defects and the higher-order chromatin structure of frozen and thawed cells with and without cryoprotectant treatment. We found that in replicating (S phase) cells, DNA was preferentially damaged by replication fork collapse, potentially leading to DNA double strand breaks (DSBs), which represent an important source of both genome instability and defects in epigenome maintenance. This induction of DNA defects by the freeze-thaw process was not prevented by any cryoprotectant studied. Both in replicating and non-replicating cells, freezing and thawing altered the chromatin structure in a cryoprotectant-dependent manner. Interestingly, cells with condensed chromatin, which was strongly stimulated by dimethyl sulfoxide (DMSO) prior to freezing had the highest rate of survival after thawing. Our results will facilitate the design of compounds and procedures to decrease injury to cryopreserved cells.

[Enhanced Recovery Program in colorectal surgery]. / "Enhanced recovery after surgery" bevezetése a vastagbél sebészetében.

INTRODUCTION: Enhanced recovery after surgery (ERAS) programme has been described and practiced for twenty years in the perioperative management of colorectal patients. ERAS is a complex, evidence based strategy which proved to be extremely effective when linked to laparoscopy in reducing morbidity, length of hospital stay, as well as reducing cost of colorectal service. AIMS: We gradually adapted elements of ERAS protocol along with laparoscopy in the colorectal surgical treatment at a county hospital from 2013. This study reports a retrospective clinical audit of ERAS programme of two years, between 2015-2016. METHODS: In this timeframe we compared clinical results of traditional and ERAS perioperative colorectal management protocols. The two groups were assessed on the basis of demographic, cancer-related parameters and clinical outcomes. RESULTS: Over the two years of audit we treated 130 patients under "traditional" and 84 cases according to ERAS protocol. Mean length of hospital stay was 8 and 6 days median, respectively. Earlier discharge in the ERAS group did not cause any increase in the readmission rates. Morbidity (Clavien-Dindo grade 2 or more) was found to be less in ERAS group: 8,3% vs. 27,4%. ERAS programme success rate, characterized by discharge by 7th postoperative day, was over 70%, keeping well with rates of the experienced centres of ERAS. CONCLUSION: Therefore we can report a successful introduction of ERAS programme for colorectal service in a Middle-Eastern European county hospital. Based on the favourable outcome results of the retrospective audit we have extended ERAS protocol as first choice perioperative scheme for each elective colorectal case from the beginning of 2017.

Organic coating on biochar explains its nutrient retention and stimulation of soil fertility.

Amending soil with biochar (pyrolized biomass) is suggested as a globally applicable approach to address climate change and soil degradation by carbon sequestration, reducing soil-borne greenhouse-gas emissions and increasing soil nutrient retention. Biochar was shown to promote plant growth, especially when combined with nutrient-rich organic matter, e.g., co-composted biochar. Plant growth promotion was explained by slow release of nutrients, although a mechanistic understanding of nutrient storage in biochar is missing. Here we identify a complex, nutrient-rich organic coating on co-composted biochar that covers the outer and inner (pore) surfaces of biochar particles using high-resolution spectro(micro)scopy and mass spectrometry. Fast field cycling nuclear magnetic resonance, electrochemical analysis and gas adsorption demonstrated that this coating adds hydrophilicity, redox-active moieties, and additional mesoporosity, which strengthens biochar-water interactions and thus enhances nutrient retention. This implies that the functioning of biochar in soil is determined by the formation of an organic coating, rather than biochar surface oxidation, as previously suggested.

CdSe Quantum Dots Functionalized with Chiral, Thiol-Free Carboxylic Acids: Unraveling Structural Requirements for Ligand-Induced Chirality.

Functionalization of colloidal quantum dots (QDs) with chiral cysteine derivatives by phase-transfer ligand exchange proved to be a simple yet powerful method for the synthesis of chiral, optically active QDs regardless of their size and chemical composition. Here, we present induction of chirality in CdSe by thiol-free chiral carboxylic acid capping ligands (l- and d-malic and tartaric acids). Our circular dichroism (CD) and infrared experimental data showed how the presence of a chiral carboxylic acid capping ligand on the surface of CdSe QDs was necessary but not sufficient for the induction of optical activity in QDs. A chiral bis-carboxylic acid capping ligand needed to have three oxygen-donor groups during the phase-transfer ligand exchange to successfully induce chirality in CdSe. Intrinsic chirality of CdSe nanocrystals was not observed as evidenced by transmission electron microscopy and reverse phase-transfer ligand exchange with achiral 1-dodecanethiol. Density functional theory geometry optimizations and CD spectra simulations suggest an explanation for these observations. The tridentate binding via three oxygen-donor groups had an energetic preference for one of the two possible binding orientations on the QD (111) surface, leading to the CD signal. By contrast, bidentate binding was nearly equienergetic, leading to cancellation of approximately oppositely signed corresponding CD signals. The resulting induced CD of CdSe functionalized with chiral carboxylic acid capping ligands was the result of hybridization of the (achiral) QD and (chiral) ligand electronic states controlled by the ligand's absolute configuration and the ligand's geometrical arrangement on the QD surface.

Theoretical and experimental study of the antifreeze protein AFP752, trehalose and dimethyl sulfoxide cryoprotection mechanism: correlation with cryopreserved cell viability.

In this work the physico-chemical properties of selected cryoprotectants (antifreeze protein TrxA-AFP752, trehalose and dimethyl sulfoxide) were correlated with their impact on the constitution of ice and influence on frozen/thawed cell viability. The freezing processes and states of investigated materials solutions were described and explained from a fundamental point of view using ab-initio modelling (molecular dynamics, DFT), Raman spectroscopy, Differential Scanning Calorimetry and X-Ray Diffraction. For the first time, in this work we correlated the microscopic view (modelling) with the description of the frozen solution states and put these results in the context of human skin fibroblast viability after freezing and thawing. DMSO and AFP had different impacts on their solution's freezing process but in both cases the ice crystallinity size was considerably reduced. DMSO and AFP treatment in different ways improved the viability of frozen/thawed cells.

Caulobacter PopZ forms an intrinsically disordered hub in organizing bacterial cell poles.

Despite their relative simplicity, bacteria have complex anatomy at the subcellular level. At the cell poles of Caulobacter crescentus, a 177-amino acid (aa) protein called PopZ self-assembles into 3D polymeric superstructures. Remarkably, we find that this assemblage interacts directly with at least eight different proteins, which are involved in cell cycle regulation and chromosome segregation. The binding determinants within PopZ include 24 aa at the N terminus, a 32-aa region near the C-terminal homo-oligomeric assembly domain, and portions of an intervening linker region. Together, the N-terminal 133 aa of PopZ are sufficient for interacting with all binding partners, even in the absence of homo-oligomeric assembly. Structural analysis of this region revealed that it is intrinsically disordered, similar to p53 and other hub proteins that organize complex signaling networks in eukaryotic cells. Through live-cell photobleaching, we find rapid binding kinetics between PopZ and its partners, suggesting many pole-localized proteins become concentrated at cell poles through rapid cycles of binding and unbinding within the PopZ scaffold. We conclude that some bacteria, similar to their eukaryotic counterparts, use intrinsically disordered hub proteins for network assembly and subcellular organization.

Chirality Inversion of CdSe and CdS Quantum Dots without Changing the Stereochemistry of the Capping Ligand.

L-cysteine derivatives induce and modulate the optical activity of achiral cadmium selenide (CdSe) and cadmium sulfide (CdS) quantum dots (QDs). Remarkably, N-acetyl-L-cysteine-CdSe and L-homocysteine-CdSe as well as N-acetyl-L-cysteine-CdS and L-cysteine-CdS showed "mirror-image" circular dichroism (CD) spectra regardless of the diameter of the QDs. This is an example of the inversion of the CD signal of QDs by alteration of the ligand's structure, rather than inversion of the ligand's absolute configuration. Non-empirical quantum chemical simulations of the CD spectra were able to reproduce the experimentally observed sign patterns and demonstrate that the inversion of chirality originated from different binding arrangements of N-acetyl-L-cysteine and L-homocysteine-CdSe to the QD surface. These efforts may allow the prediction of the ligand-induced chiroptical activity of QDs by calculating the specific binding modes of the chiral capping ligands. Combined with the large pool of available chiral ligands, our work opens a robust approach to the rational design of chiral semiconducting nanomaterials.

The effects of high concentrations of ionic liquid on GB1 protein structure and dynamics probed by high-resolution magic-angle-spinning NMR spectroscopy.

Ionic liquids have great potential in biological applications and biocatalysis, as some ionic liquids can stabilize proteins and enhance enzyme activity, while others have the opposite effect. However, on the molecular level, probing ionic liquid interactions with proteins, especially in solutions containing high concentration of ionic liquids, has been challenging. In the present work the 13C, 15N-enriched GB1 model protein was used to demonstrate applicability of high-resolution magic-angle-spinning (HR-MAS) NMR spectroscopy to investigate ionic liquid - protein interactions. Effect of an ionic liquid (1-butyl-3-methylimidazolium bromide, [C4-mim]Br) on GB1was studied over a wide range of the ionic liquid concentrations (0.6 to 3.5 M, which corresponds to 10%-60% v/v). Interactions between GB1 and [C4-mim]Br were observed from changes in the chemical shifts of the protein backbone as well as the changes in 15N ps-ns dynamics and rotational correlation times. Site-specific interactions between the protein and [C4-mim]Br were assigned using 3D methods under HR-MAS conditions. Thus, HR-MAS NMR is a viable tool that could aid in elucidation of the molecular mechanism of ionic liquid - protein interactions.

¹³C- and ¹H-detection under fast MAS for the study of poorly available proteins: application to sub-milligram quantities of a 7 trans-membrane protein.

We demonstrate that (13)C-detected spectra recorded using fast (60 kHz) magic angle spinning on sub-milligram (<10 µmol) quantities of a protonated 7 trans-membrane helix protein (bacteriorhodopsin) in its native lipid environment are comparable in sensitivity and resolution to those recorded using 15-fold larger sample volumes with conventional solid state NMR methodology. We demonstrate the utility of proton-detected measurements which yield narrow (1)H linewidths under these conditions, and that no structural alterations are observed. We propose that these methods will prove useful to gain structural information on membrane proteins with poor availability, which can be studied in their native lipid environments.

Ligand induced circular dichroism and circularly polarized luminescence in CdSe quantum dots.

Chiral thiol capping ligands L- and D-cysteines induced modular chiroptical properties in achiral cadmium selenide quantum dots (CdSe QDs). Cys-CdSe prepared from achiral oleic acid capped CdSe by postsynthetic ligand exchange displayed size-dependent electronic circular dichroism (CD) and circularly polarized luminescence (CPL). Opposite CPL signals were measured for the CdSe QDs capped with D- and L-cysteine. The CD profile and CD anisotropy varied with size of CdSe nanocrystals with largest anisotropy observed for CdSe nanoparticles of 4.4 nm. Magic angle spinning solid state NMR (MAS ssNMR) experiments suggested bidentate interaction between cysteine and the surface of CdSe. Time Dependent Density Functional Theory (TDDFT) calculations verified that attachment of L- and D-cysteine to the surface of model (CdSe)13 nanoclusters induces measurable opposite CD signals for the exitonic band of the nanocluster. The origin of the induced chirality is consistent with the hybridization of highest occupied CdSe molecular orbitals with those of the chiral ligand.

Achiral CdSe quantum dots exhibit optical activity in the visible region upon post-synthetic ligand exchange with D- or L-cysteine.

Semiconductor cadmium selenide (CdSe) quantum dots (QDs) exhibited mirror-image circular dichroism (CD) spectra in the visible region (350-570 nm) after replacing the trioctylphosphine oxide/oleic acid ligands on achiral nanocrystals with D- and L-cysteines. Chiroptical properties of cysteine-capped CdSe QDs depend on their size and can be fine-tuned by changing the radius of QDs.