Controlling the Structure of Carbon Deposit by Nitrogen Doping Catalytic Chemical Vapor Deposition Synthesis

Nitrogen doped multi-walled carbon nanotubes and other carbon nanoparticles were synthesized by catalytic chemical vapor deposition of tripropylamine and acetylene on CaCO₃-supported cobalt catalyst (5 wt%), prepared by impregnation, and various precursors. Each synthesis was performed by using either the pure nitrogenous organic compound or its mixture with acetone. Transmission electron microscopy studies revealed a significant difference both in the yield and the diversity of the carbon deposits. Every synthesis resulted in bamboo-like nanotubes, and nearly all of them also in onion-like structures. Electron energy loss spectroscopy studies of the samples indicated the presence of nitrogen and calcium (caused by the catalyst support). High-resolution transmission electron microscopy and X-ray diffraction measurements were also performed to characterize the samples.

Large Stokes-shift bioorthogonal probes for STED, 2P-STED and multi-color STED nanoscopy

Synthesis and multiple STED imaging applications of four, red-emitting (610-670 nm), tetrazine-functionalized fluorescent probes (CBRD = Chemical Biology Research group Dye 1-4) with large Stokes-shift is presented. Present studies revealed the super-resolution microscopy applicability of the probes as demonstrated through bioorthogonal labeling scheme of cytoskeletal proteins actin and keratin-19, and mitochondrial protein TOMM20. Furthermore, super-resolved images of insulin receptors in live-cell bioorthogonal labeling schemes through a genetically encoded cyclooctynylated non-canonical amino acid are also presented. The large Stokes-shifts and the wide spectral bands of the probes enabled the use of two common depletion lasers (660 nm and 775 nm). The probes were also found suitable for super-resolution microscopy in combination with two-photon excitation (2P-STED) resulting in improved spatial resolution. One of the dyes was also used together with two commercial dyes in the three-color STED imaging of intracellular structures.

Synergistic transport of a fluorescent coumarin probe marks coumarins as pharmacological modulators of Organic anion-transporting polypeptide, OATP3A1

Organic anion-transporting polypeptide 3A1 (OATP3A1) is a membrane transporter mediating the cellular uptake of various hormones such as estrone-3-sulfate, prostaglandins E1 and E2 and thyroxine. OATP3A1 is widely expressed in the human body and its presence in tissue-blood barriers, neurons and muscle cells marks it as a potential pharmacological target. Herein we demonstrate that an otherwise membrane impermeant, zwitterionic fluorescent coumarin probe, bearing a sulfonate function is a potent substrate of human OATP3A1, thus readily transported into HEK-293-OATP3A1 cells allowing functional investigation and the screen of drug interactions of the OATP3A1 transporter. At the same time, dyes lacking either the sulfonate motif or the coumarin scaffold showed a dramatic decrease in affinity or even a complete loss of transport. Furthermore, we observed a distinct inhibition/activation pattern in the OATP3A1-mediated uptake of closely related fluorescent coumarin derivatives differing only in the presence of the sulfonate moiety. Additionally, we detected a synergistic effect between one of the probes tested and the endogenous OATP substrate estrone-3-sulfate. These data, together with docking results indicate the presence of at least two cooperative substrate binding sites in OATP3A1. Besides providing the first sensitive probe for testing OATP3A1 substrate/inhibitor interactions, our results also help to understand substrate recognition and transport mechanism of the poorly characterized OATP3A1. Moreover, coumarins are good candidates for OATP3A1-targeted drug delivery and as pharmacological modulators of OATP3A1.

In Situ Metabolic Characterisation of Breast Cancer and Its Potential Impact on Therapy

In spite of tremendous developments in breast cancer treatment, the relatively high incidence of relapsing cases indicates a great need to find new therapeutic strategies in recurrent, metastatic and advanced cases. The bioenergetic needs of growing tumours at the primary site or in metastases-accumulating genomic alterations and further heterogeneity-are supported by metabolic rewiring, an important hallmark of cancer. Adaptation mechanisms as well as altered anabolic and catabolic processes balance according to available nutrients, energy, oxygen demand and overgrowth or therapeutic resistance. Mammalian target of rapamycin (mTOR) hyperactivity may contribute to this metabolic plasticity and progression in breast carcinomas. We set out to assess the metabolic complexity in breast cancer cell lines and primary breast cancer cases. Cellular metabolism and mTOR-related protein expression were characterised in ten cell lines, along with their sensitivity to specific mTOR and other metabolic inhibitors. Selected immunohistochemical reactions were performed on ~100 surgically removed breast cancer specimens. The obtained protein expression scores were correlated with survival and other clinicopathological data. Metabolic and mTOR inhibitor mono-treatments had moderate antiproliferative effects in the studied cell lines in a subtype-independent manner, revealing their high adaptive capacity and survival/growth potential. Immunohistochemical analysis of p-S6, Rictor, lactate dehydrogenase A, glutaminase, fatty acid synthase and carnitine palmitoyltransferase 1A in human samples identified high mTOR activity and potential metabolic plasticity as negative prognostic factors for breast cancer patients, even in subtypes generally considered as low-risk. According to our results, breast cancer is characterised by considerable metabolic diversity, which can be targeted by combining antimetabolic treatments and recent therapies. Alterations in these pathways may provide novel targets for future drug development in breast cancer. We also propose a set of immunostainings for scoring metabolic heterogeneity in individual cases in order to select patients who may benefit from more accurate follow-up and specific therapies.

Conditionally Activatable Visible-Light Photocages

The proof of concept for conditionally activatable photocages is demonstrated on a new vinyltetrazine-derivatized coumarin. The tetrazine form is disabled in terms of light-induced cargo release, however, bioorthogonal transformation of the modulating tetrazine moiety results in fully restored photoresponsivity. Irradiation of such a “click-armed” photocage with blue light leads to fast and efficient release of a set of caged model species, conjugated via various linkages. Live-cell applicability of the concept was also demonstrated by the conditional release of a fluorogenic probe using mitochondrial pretargeting.

Microscope laser assisted photooxidative activation of bioorthogonal ClickOx probes

A photoactivatable fluorogenic tetrazine-rhodaphenothiazine probe was synthesized and studied in light-assisted, bioorthogonal labeling schemes. Experimental results revealed that the bioorthogonally conjugated probe efficiently sensitizes ¹O₂ generation upon illumination with green or orange light and undergoes self-oxidation leading to an intensely fluorescent sulfoxide product. An added value of the present probe is that it is also suitable for STED super-resolution microscopy using a 660 nm depletion laser.

A Bioorthogonally Applicable, Fluorogenic, Large Stokes-Shift Probe for Intracellular Super-Resolution Imaging of Proteins

Herein, we present the synthesis and application of a fluorogenic, large Stokes-shift (>100 nm), bioorthogonally conjugatable, membrane-permeable tetrazine probe, which can be excited at common laser line 488 nm and detected at around 600 nm. The applied design enabled improved fluorogenicity in the orange/red emission range, thus efficient suppression of background and autofluorescence upon imaging biological samples. Moreover, unlike our previous advanced probes, it does not require the presence of special target platforms or microenvironments to achieve similar fluorogenicity and can be generally applied, e.g., on translationally bioorthogonalized proteins. Live-cell labeling schemes revealed that the fluorogenic probe is suitable for specific labeling of intracellular proteins, site-specifically modified with a cyclooctynylated, non-canonical amino acid, even under no-wash conditions. Furthermore, the probe was found to be applicable in stimulated emission depletion (STED) super-resolution microscopy imaging using a 660 nm depletion laser. Probably the most salient feature of this new probe is that the large Stokes-shift allows dual-color labeling schemes of cellular structures using distinct excitation and the same detection wavelengths for the combined probes, which circumvents chromatic aberration related problems.

Twisted paddlewheel rhodium complexes: Contribution of central and axial chirality to ECD, VCD, and NMR spectra

Dirhodium complexes bearing N-substituted chiral amino acid ligands are investigated. These complexes have an unusual twisted paddlewheel structure, showing inherent chirality. We would like to demonstrate that parallel application of chiroptical spectroscopic methods (ECD and VCD) and NMR spectroscopy combined with quantum chemical calculations constitutes a powerful tool to determine the configuration of the complexes unequivocally. Two chiroptical methods are needed to determine the absolute configuration: ECD for the coordinated nitrogen atom and VCD for the rhodium core. A quick to use NMR method is also presented: Upon the coordination of small molecules in the axial position, the relative configuration of both the rhodium core and the nitrogen atom can be determined simultaneously by studying spatial proximities provided by 1D NOE spectra.

Next-generation sequencing identifies novel mitochondrial variants in pituitary adenomas

PURPOSE

Disrupted mitochondrial functions and genetic variants of mitochondrial DNA (mtDNA) have been observed in different human neoplasms. Next-generation sequencing (NGS) can be used to detect even low heteroplasmy-level mtDNA variants. We aimed to investigate the mitochondrial genome in pituitary adenomas by NGS.

METHODS

We analysed 11 growth hormone producing and 33 non-functioning [22 gonadotroph and 11 hormone immunonegative] pituitary adenomas using VariantPro™ Mitochondrion Panel on Illumina MiSeq instrument. Revised Cambridge Reference Sequence (rCRS) of the mtDNA was used as reference. Heteroplasmy was determined using a 3% cutoff.

RESULTS

496 variants were identified in pituitary adenomas with overall low level of heteroplasmy (7.22%). On average, 35 variants were detected per sample. Samples harbouring the highest number of variants had the highest Ki-67 indices independently of histological subtypes. We identified eight variants (A11251G, T4216C, T16126C, C15452A, T14798C, A188G, G185A, and T16093C) with different prevalences among different histological groups. T16189C was found in 40% of non-recurrent adenomas, while it was not present in the recurrent ones. T14798C and T4216C were confirmed by Sanger sequencing in all 44 samples. 100% concordance was found between NGS and Sanger method.

CONCLUSIONS

NGS is a reliable method for investigating mitochondrial genome and heteroplasmy in pituitary adenomas. Out of the 496 detected variants, 414 have not been previously reported in pituitary adenoma. The high number of mtDNA variants may contribute to adenoma genesis, and some variants (i.e., T16189C) might associate with benign behaviour.

Synthesis of (1,2,3-triazol-4-yl)methyl Phosphinates and (1,2,3-Triazol-4-yl)methyl Phosphates by Copper-Catalyzed Azide-Alkyne Cycloaddition

An efficient and practical method was developed for the synthesis of new (1,2,3triazol4yl)methyl phosphinates and (1,2,3-triazol-4-yl)methyl phosphates by the copper(I)catalyzed azide-alkyne cycloaddition (CuAAC) of organic azides and prop-2-ynyl phosphinate or prop-2-ynyl phosphate. The synthesis of (1benzyl-1H-1,2,3-triazol-4-yl)methyl diphenylphosphinate was optimized with respect to the reaction parameters, such as the temperature, reaction time, and catalyst loading. The approach was applied to a range of organic azides, which confirmed the wide scope and the substituent tolerance of the process. The method elaborated represents a novel approach for the synthesis of the target compounds.

Tracking down protein-protein interactions via a FRET-system using site-specific thiol-labeling

Förster resonance energy transfer is among the most popular tools to follow protein-protein interactions. Although limited to certain cases, site-specific fluorescent labeling of proteins via natural functions by means of chemical manipulations can redeem laborious protein engineering techniques. Herein we report on the synthesis of a heterobifunctional tag and its use in site-specific protein labeling studies aiming at exploring protein-protein interactions. The oxadiazole-methylsulfonyl functionality serves as a thiol specific warhead that enables easy and selective installation of fluorescent labels through a bioorthogonal motif. Mitogen activated protein kinase (MAPK14) and its substrate mitogen activated protein kinase activated kinase (MAPKAP2) or its docking motif, a 22 amino acid-long peptide fragment, were labeled with a donor and an acceptor, respectively. Evolution of strong FRET signals upon protein-protein interactions supported the specific communication between the partners. Using an efficient FRET pair allowed the estimation of dissociation constants for protein-protein and peptide-protein interactions (145 nM and 240 nM, respectively).

A rapid and concise setup for the fast screening of FRET pairs using bioorthogonalized fluorescent dyes

One of the most popular means to follow interactions between bio(macro)molecules is Förster resonance energy transfer (FRET). There is large interest in widening the selection of fluorescent FRET pairs especially in the region of the red/far red range, where minimal autofluorescence is encountered. A set of bioorthogonally applicable fluorescent dyes, synthesized recently in our lab, were paired (Cy3T/Cy5T; Cy1A/Cy3T and Cy1A/CBRD1A) based on their spectral characteristics in order to test their potential in FRET applications. For fast elaboration of the selected pairs we have created a bioorthogonalized platform based on complementary 17-mer DNA oligomers. The cyclooctynylated strands were modified nearly quantitatively with the fluorophores via bioorthogonal chemistry steps, using azide- (Cy1; CBRD1) or tetrazine-modified (Cy3; Cy5) dyes. Reactions were followed by capillary electrophoresis using a method specifically developed for this project. FRET efficiencies of the fluorescent dye pairs were compared both in close proximity (5' and 3' matched) and at larger distance (5' and 5' matched). The specificity of FRET signals was further elaborated by denaturation and competition studies. Cy1A/Cy3T and Cy1A/CBRD1A introduced here as novel FRET pairs are highly recommended for FRET applications based on the significant changes in fluorescence intensities of the donor and acceptor peaks. Application of one of the FRET pairs was demonstrated in live cells, transfected with labeled oligos. Furthermore, the concise installation of the dyes allows for efficient fluorescence modification of any selected DNA strands as was demonstrated in the construction of Cy3T labeled oligomers, which were used in the FISH-based detection of Helicobacter pylori.

[Steroid 21-hydroxylase deficiency, the most frequent cause of congenital adrenal hyperplasia]

Congenital adrenal hyperplasia is a group of genetic diseases due to the disablement of 7 genes; one of them is steroid 21-hydroxylase deficiency. The genes of congenital adrenal hyperplasia encode enzymes taking part in the steroidogenesis of adrenal gland. Steroid 21-hydroxylase deficiency is an autosomal recessive disorder caused by mutations of the steroid 21-hydroxylase gene. The mutations of steroid 21-hydroxylase gene cause 95% of the congenital adrenal hyperplasia cases. Although the non-classic steroid 21-hydroxylase deficiency with mild symptoms is seldom diagnosed, the classic steroid 21-hydroxylase deficiency may lead to life-threatening salt-wasting and adrenal crises due to the insufficient aldosterone and cortisol serum levels. The classic type requires life-long steroid replacement which may result in cushingoid side effects, and typical comorbidities may be also developed. The patients' quality of life is decreased, and their mortality is much higher than that of the population without steroid 21-hydroxylase deficiency. The diagnosis, consequences and the patients' life-long clinical care require a multidisciplinary approach: the specialists in pediatrics, internal medicine, endocrinology, laboratory medicine, genetic diagnostics, surgery, obstetrics-gynecology and psychology need to work together. Orv Hetil. 2018; 159(7): 269-277.

Capillary electrophoresis study on the base-catalyzed formation of bioactive oxidized metabolites of 20-hydroxyecdysone

A novel capillary electrophoretic method was developed for the analysis and monitoring of the base-catalyzed autoxidation of 20-hydroxyecdysone, a worldwide used non-hormonal anabolic food supplement. An effective separation of the starting material and its bioactive oxidized derivatives was achieved by using sulfobutyl-β-cyclodextrin as selector at pH 11 and by fixing the separation voltage at +30kV. Only a dilution step was inserted before injecting the sample, taken from the crude reaction mixture, to the capillary electrophoresis instrument. The same alkaline pH was used for the analysis as for the reaction, unlike the previously reported HPLC study where sample neutralization was required prior to the measurement. Due to the very short analysis time (6min) in capillary electrophoresis, more frequent sampling and more detailed time scale analysis could be carried out. Furthermore, in contrast with the preceding HPLC results, the previously unobserved calonysterone could also be detected by capillary electrophoresis as a minor primary product. Our novel method demonstrated higher resolution than the one before. Baseline separation could be achieved and the resolution values were in the range of 1.9-7.0. The limit of detection was below 71μg/ml, the relative standard deviation values of the migration time and peak area for intra- and inter-day precision were less than 10%. The more precise, direct monitoring of the time dependency of the oxidation process is expected to have a significant impact on yield optimization initiatives to allow related pharmacological studies in the near future.

Altered neurite morphology and cholinergic function of induced pluripotent stem cell-derived neurons from a patient with Kleefstra syndrome and autism

The aim of the present study was to establish an in vitro Kleefstra syndrome (KS) disease model using the human induced pluripotent stem cell (hiPSC) technology. Previously, an autism spectrum disorder (ASD) patient with Kleefstra syndrome (KS-ASD) carrying a deleterious premature termination codon mutation in the EHMT1 gene was identified. Patient specific hiPSCs generated from peripheral blood mononuclear cells of the KS-ASD patient were differentiated into post-mitotic cortical neurons. Lower levels of EHMT1 mRNA as well as protein expression were confirmed in these cells. Morphological analysis on neuronal cells differentiated from the KS-ASD patient-derived hiPSC clones showed significantly shorter neurites and reduced arborization compared to cells generated from healthy controls. Moreover, density of dendritic protrusions of neuronal cells derived from KS-ASD hiPSCs was lower than that of control cells. Synaptic connections and spontaneous neuronal activity measured by live cell calcium imaging could be detected after 5 weeks of differentiation, when KS-ASD cells exhibited higher sensitivity of calcium responses to acetylcholine stimulation indicating a lower nicotinic cholinergic tone at baseline condition in KS-ASD cells. In addition, gene expression profiling of differentiated neuronal cells from the KS-ASD patient revealed higher expression of proliferation-related genes and lower mRNA levels of genes involved in neuronal maturation and migration. Our data demonstrate anomalous neuronal morphology, functional activity and gene expression in KS-ASD patient-specific hiPSC-derived neuronal cultures, which offers an in vitro system that contributes to a better understanding of KS and potentially other neurodevelopmental disorders including ASD.

Expression of G protein-coupled oestrogen receptor in melanoma and in pregnancy-associated melanoma

BACKGROUND

The hormone sensitivity of melanoma and the role of 'classical' oestrogen receptor (ER) α and β in tumour progression have been intensively studied with rather contradictory results. The presence of 'non-classical' G protein-coupled oestrogen receptor (GPER) has not been investigated on human melanoma tissues.

OBJECTIVE

To analyse the expression of GPER, ERα and ERβ in pregnancy-associated (PAM) and in non-pregnancy-associated (NPAM) melanomas in correlation with traditional prognostic markers and disease-free survival (DFS).

METHODS

Receptor protein levels were tested using immunohistochemistry in 81 formalin-fixed paraffin-embedded melanoma tissues. PAMs (n = 38) were compared with age- and Breslow thickness-matched cases (n = 43) including non-pregnant women (NPAM-W) (n = 22) and men (NPAM-M) (n = 21). The association between receptor expression and DFS was analysed by uni- and multivariate Cox proportional hazards regression.

RESULTS

G protein-coupled oestrogen receptor was detected both in PAMs and NPAMs. In 39 of the 41 (95.1%) GPER-positive melanomas, GPER and ERβ were co-expressed. GPER/ERβ-positive melanomas were significantly more common in PAM compared to NPAM (P = 0.0001) with no significant difference between genders (P = 0.4383). In PAMs, the distribution of GPER and ERβ was similar (78.4% vs. 81.6%; P = 0.8504), while in NPAM, ERβ was the representative ER (60.5% vs. 27.9%; P = 0.0010) without gender difference (59.1% vs. 61.9%). GPER-/ERβ-positive melanomas were associated with lower Breslow thickness, lower mitotic rate and higher presence of peritumoral lymphocyte infiltration (PLI) compared to GPER-/ERβ-negative cases (P = 0.0156, P = 0.0036 and P = 0.0001) predicting a better DFS (HR = 0.785, 95% CI 0.582-1.058). Despite the significantly higher frequency of GPER and ERβ expression in PAM, no significant difference was found in DFS between PAM and NPAM. All but one case failed to show ERα expression.

CONCLUSIONS

The presence of GPER and its simultaneous expression with ERβ can serve as a new prognostic indicator in a significant subpopulation of melanoma patients.

Bisazide Cyanine Dyes as Fluorogenic Probes for Bis-Cyclooctynylated Peptide Tags and as Fluorogenic Cross-Linkers of Cyclooctynylated Proteins

Herein we present the synthesis and fluorogenic characterization of a series of double-quenched bisazide cyanine probes with emission maxima between 565 and 580 nm that can participate in covalent, two-point binding bioorthogonal tagging schemes in combination with bis-cyclooctynylated peptides. Compared to other fluorogenic cyanines, these double-quenched systems showed remarkable fluorescence intensity increase upon formation of cyclic dye-peptide conjugates. Furthermore, we also demonstrated that these bisazides are useful fluorogenic cross-linking platforms that are able to form a covalent linkage between monocyclooctynylated proteins.

Correction: A systematic study of protein labeling by fluorogenic probes using cysteine targeting vinyl sulfone-cyclooctyne tags

Correction for 'A systematic study of protein labeling by fluorogenic probes using cysteine targeting vinyl sulfone-cyclooctyne tags' by B. Söveges, et al., Org. Biomol. Chem., 2016, 14, 6071-6078.