Characterization of a novel 4-guanidinobutyrase from Candida parapsilosis.

Enzymes of the ureohydrolase superfamily are specific in recognizing their substrates. While looking to broaden the substrate specificity of 4-guanidinobutyrase (GBase), we isolated a yeast, typed as Candida parapsilosis (NCIM 3689), that efficiently utilized both 4-guanidinobutyrate (GB) and 3-guanidinopropionate (GP) as a sole source of nitrogen. A putative GBase sequence was identified from its genome upon pBLAST query using the GBase sequence from Aspergillus niger (AnGBase). The C. parapsilosis GBase (CpGBase) ORF was PCR amplified, cloned, and sequenced. Further, the functional CpGBase protein expressed in Saccharomyces cerevisiae functioned as GBase and 3-guanidinopropionase (GPase). S. cerevisiae cannot grow on GB or GP. However, the transformants expressing CpGBase acquired the ability to utilize and grow on both GB and GP. The expressed CpGBase protein was enriched and analyzed for substrate saturation and product inhibition by γ-aminobutyric acid and ß-alanine. In contrast to the well-characterized AnGBase, CpGBase from C. parapsilosis is a novel ureohydrolase and showed hyperbolic saturation for GB and GP with comparable efficiency (Vmax/KM values of 3.4 and 2.0, respectively). With the paucity of structural information and limited active site data available on ureohydrolases, CpGBase offers an excellent paradigm to explore this class of enzymes.

Next generation of boron neutron capture therapy (BNCT) agents for cancer treatment.

Boron neutron capture therapy (BNCT) is one of the most promising treatments among neutron capture therapies due to its long-term clinical application and unequivocally obtained success during clinical trials. Boron drug and neutron play an equivalent crucial role in BNCT. Nevertheless, current clinically used l-boronophenylalanine (BPA) and sodium borocaptate (BSH) suffer from large uptake dose and low blood to tumor selectivity, and that initiated overwhelm screening of next generation of BNCT agents. Various boron agents, such as small molecules and macro/nano-vehicles, have been explored with better success. In this featured article, different types of agents are rationally analyzed and compared, and the feasible targets are shared to present a perspective view for the future of BNCT in cancer treatment. This review aims at summarizing the current knowledge of a variety of boron compounds, reported recently, for the application of BCNT.

Molecular insights into the inhibition of glutamate dehydrogenase by the dicarboxylic acid metabolites.

Glutamate dehydrogenase (GDH) is a salient metabolic enzyme which catalyzes the NAD+ - or NADP+ -dependent reversible conversion of α-ketoglutarate (AKG) to l-glutamate; and thereby connects the carbon and nitrogen metabolism cycles in all living organisms. The function of GDH is extensively regulated by both metabolites (citrate, succinate, etc.) and non-metabolites (ATP, NADH, etc.) but sufficient molecular evidences are lacking to rationalize the inhibitory effects by the metabolites. We have expressed and purified NADP+ -dependent Aspergillus terreus GDH (AtGDH) in recombinant form. Succinate, malonate, maleate, fumarate, and tartrate independently inhibit the activity of AtGDH to different extents. The crystal structures of AtGDH complexed with the dicarboxylic acid metabolites and the coenzyme NADPH have been determined. Although AtGDH structures are not complexed with substrate; surprisingly, they acquire super closed conformation like previously reported for substrate and coenzyme bound catalytically competent Aspergillus niger GDH (AnGDH). These dicarboxylic acid metabolites partially occupy the same binding pocket as substrate; but interact with varying polar interactions and the coenzyme NADPH binds to the Domain-II of AtGDH. The low inhibition potential of tartrate as compared to other dicarboxylic acid metabolites is due to its weaker interactions of carboxylate groups with AtGDH. Our results suggest that the length of carbon skeleton and positioning of the carboxylate groups of inhibitors between two conserved lysine residues at the GDH active site might be the determinants of their inhibitory potency. Molecular details on the dicarboxylic acid metabolites bound AtGDH active site architecture presented here would be applicable to GDHs in general.

Environmental role of aromatic carboxylesterases.

The carboxylesterases (EC 3.1.1.x) are widely distributed and form an important yet diverse group of hydrolases catalysing the ester bond cleavage in a variety of substrates. Besides acting on plant cell wall components like cutin, tannin and feruloyl esters, they are often the first line of defence to metabolize drugs, xenobiotics, pesticides, insecticides and plastic. But for the promiscuity of some carboxylesterases and cutinases, very few enzymes act exclusively on aromatic carboxylic acid esters. Infrequent occurrence of aromatic carboxylesterases suggests that aromatic carboxylesters are inherently more difficult to hydrolyse than the regular carboxylesters because of both steric and polar effects. Naturally occurring aromatic carboxylesters were rare before the anthropogenic activity augmented their environmental presence and diversity. An appraisal of the literature shows that the hydrolysis of aromatic carboxylic esters is a uniquely difficult endeavour and hence deserves special attention. Enzymes to hydrolyse such esters are evolving rapidly in nature. Very few such enzymes are known and they often display much lower catalytic efficiencies. Obviously, the esters of aromatic carboxylic acids, including polyethylene terephthalate waste, pose an environmental challenge. In this review, we highlight the uniqueness of aromatic carboxylesters and then underscore the importance of relevant carboxylesterases.

Recent Advances in BODIPY Compounds: Synthetic Methods, Optical and Nonlinear Optical Properties, and Their Medical Applications.

Organoboron compounds are attracting immense research interest due to their wide range of applications. Particularly, low-coordinate organoboron complexes are receiving more attention due to their improbable optical and nonlinear optical properties, which makes them better candidates for medical applications. In this review, we summarize the various synthetic methods including multicomponent reactions, microwave-assisted and traditional pathways of organoboron complexes, and their optical and nonlinear properties. This review also includes the usage of organoboron complexes in various fields including biomedical applications.

The Role of Microbiome in Brain Development and Neurodegenerative Diseases.

Hundreds of billions of commensal microorganisms live in and on our bodies, most of which colonize the gut shortly after birth and stay there for the rest of our lives. In animal models, bidirectional communications between the central nervous system and gut microbiota (Gut-Brain Axis) have been extensively studied, and it is clear that changes in microbiota composition play a vital role in the pathogenesis of various neurodevelopmental and neurodegenerative disorders, such as Autism Spectrum Disorder, Alzheimer's disease, Parkinson's disease, Multiple Sclerosis, Amyotrophic Lateral Sclerosis, anxiety, stress, and so on. The makeup of the microbiome is impacted by a variety of factors, such as genetics, health status, method of delivery, environment, nutrition, and exercise, and the present understanding of the role of gut microbiota and its metabolites in the preservation of brain functioning and the development of the aforementioned neurological illnesses is summarized in this review article. Furthermore, we discuss current breakthroughs in the use of probiotics, prebiotics, and synbiotics to address neurological illnesses. Moreover, we also discussed the role of boron-based diet in memory, boron and microbiome relation, boron as anti-inflammatory agents, and boron in neurodegenerative diseases. In addition, in the coming years, boron reagents will play a significant role to improve dysbiosis and will open new areas for researchers.

Self-Assembled Monolayer of Monomercaptoundecahydro-closo-dodecaborate on a Polycrystalline Gold Surface.

In this work, we present an electrochemical study of the boron cage monomercaptoundecahydro-closo-dodecaborate [B12H11SH]2- in solution and in a self-assembled monolayer over a polycrystalline gold electrode. Cyclic voltammetry of the anion [B12H11SH]2- in solution showed a shift in the peak potentials related to the redox processes of gold hydroxides, which evidences the interaction between the boron cage and the gold surface. For an Au electrode modified with the anion [B12H11SH]2-, cyclic voltammetry response of the probe Fe(CN)63-/Fe(CN)64- showed a ΔEp value typical for a surface modification. Electrochemical impedance spectroscopy presented Rtc and Cdl values related to the formation of a self-assembled monolayer (SAM). A comparison of electrochemical responses of a modified electrode with thioglycolic acid (TGA) reveals that the boron cage [B12H11SH]2- diminishes the actives sites over the Au surface due to the steric effects. Differential capacitance measurements for bare gold electrode and those modified with [B12H11SH]2- and (TGA), indicate that bulky thiols enhance charge accumulation at the electrode-solution interface. In addition to electrochemical experiments, DFT calculations and surface plasmon resonance measurements (SPR) were carried out to obtain quantum chemical descriptors and to evaluate the molecular length and the dielectric constant of the Boron cage. From SPR experiments, the adsorption kinetics of [B12H11SH]2- were studied. The data fit for a Langmuir kinetic equation, typical for the formation of a monolayer.

Boron Chemicals in Drug Discovery and Development: Synthesis and Medicinal Perspective.

A standard goal of medicinal chemists has been to discover efficient and potent drug candidates with specific enzyme-inhibitor abilities. In this regard, boron-based bioactive compounds have provided amphiphilic properties to facilitate interaction with protein targets. Indeed, the spectrum of boron-based entities as drug candidates against many diseases has grown tremendously since the first clinically tested boron-based drug, Velcade. In this review, we collectively represent the current boron-containing drug candidates, boron-containing retinoids, benzoxaboroles, aminoboronic acid, carboranes, and BODIPY, for the treatment of different human diseases.In addition, we also describe the synthesis, key structure-activity relationship, and associated biological activities, such as antimicrobial, antituberculosis, antitumor, antiparasitic, antiprotozoal, anti-inflammatory, antifolate, antidepressant, antiallergic, anesthetic, and anti-Alzheimer's agents, as well as proteasome and lipogenic inhibitors. This compilation could be very useful in the exploration of novel boron-derived compounds against different diseases, with promising efficacy and lesser side effects.

Organoboron Compounds: Effective Antibacterial and Antiparasitic Agents.

The unique electron deficiency and coordination property of boron led to a wide range of applications in chemistry, energy research, materials science and the life sciences. The use of boron-containing compounds as pharmaceutical agents has a long history, and recent developments have produced encouraging strides. Boron agents have been used for both radiotherapy and chemotherapy. In radiotherapy, boron neutron capture therapy (BNCT) has been investigated to treat various types of tumors, such as glioblastoma multiforme (GBM) of brain, head and neck tumors, etc. Boron agents playing essential roles in such treatments and other well-established areas have been discussed elsewhere. Organoboron compounds used to treat various diseases besides tumor treatments through BNCT technology have also marked an important milestone. Following the clinical introduction of bortezomib as an anti-cancer agent, benzoxaborole drugs, tavaborole and crisaborole, have been approved for clinical use in the treatments of onychomycosis and atopic dermatitis. Some heterocyclic organoboron compounds represent potentially promising candidates for anti-infective drugs. This review highlights the clinical applications and perspectives of organoboron compounds with the natural boron atoms in disease treatments without neutron irradiation. The main topic focuses on the therapeutic applications of organoboron compounds in the diseases of tuberculosis and antifungal activity, malaria, neglected tropical diseases and cryptosporidiosis and toxoplasmosis.

Boron-Containing Lipids and Liposomes: New Conjugates of Cholesterol with Polyhedral Boron Hydrides.

A series of boron-containing lipids were prepared by reactions of cyclic oxonium derivatives of polyhedron boranes and metallacarboranes (closo-dodecaborate anion, cobalt and iron bis(dicarbollides)) with amine and carboxylic acids which are derived from cholesterol. Stable liposomal formulations, on the basis of synthesized boron-containing lipids, hydrogenated soybean l-α-phosphatidylcholine and (HSPC) 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DSPE-PEG) as excipients, were prepared and then characterized by dynamic light scattering (DLS) that revealed the formation of particles to be smaller than 200 nm in diameter. The resulting liposomal formulations showed moderate to excellent loading and entrapment efficiency, thus justifying the design of the compounds to fit in the lipid bilayer and ensuring ease of in vivo use for future application. The liposomal formulations based on cobalt and iron bis(dicarbollide)-based lipids were found to be nontoxic against both human breast normal epithelial cells MCF-10A and human breast cancer cells MCF-7.

Angiotensin converting enzymes ACE and ACE2 in thyroid cancer progression.

Angiotensin-converting enzymes, ACE and ACE2, play not only a pivotal role in the regulation of blood pressure, but are involved in the processes of pathophysiology, including thyroid dysfunction or progression of several neoplasia such as cancers of skin, lungs, pancreas and leukemia. However, their role in the thyroid carcinogenesis remains unknown. We examined in this study the expression of ACE and ACE2 in thyroid tissues and their possible employment as biomarkers for thyroid cancer progression. Thyroid tissues, including 14 goiters (G), 12 follicular adenomas (FA), 10 follicular thyroid carcinomas (FTC), 14 papillary thyroid carcinomas (PTC) and 11 undifferentiated thyroid carcinomas (UTC), were subjected to RT-PCR and protein analyses with primers or antibodies specific for ACE and ACE2, respectively. FA revealed significantly increased ACE compared to other groups and FTC was significantly higher than UTC. ACE2 was significantly increased in PTC in comparison to G, FA and UTC, and in FTC as compared to G. The ratio ACE/ACE2 decreased, while ACE2/ACE increased with the differentiation grade of thyroid carcinoma. ACE was significantly diminished in individuals older than 50. Both ACEs were significantly diminished in M1 patients, ACE2 additionally in higher tumor masses. ACE and ACE2 are regulated within thyroid benign and malignant tissues. As the transcript ratio between both enzymes correlate proportional with the differentiation status of thyroid cancer, ACE and ACE2 may serve as new markers for thyroid carcinoma.

Synthesis, Molecular Docking, and In Vitro Boron Neutron Capture Therapy Assay of Carboranyl Sinomenine.

In comparison with pristine sinomenine and carborane precursors, the calculations of molecular docking with matrix metalloproteinases (MMPs) and methylcarboranyl-n-butyl sinomenine showed improved interactions. Accordingly, methylcarboranyl-n-butyl sinomenine shows a high potential in the treatment of rheumatoid arthritis (RA) in the presence of slow neutrons. The reaction of potassium salt of sinomenie, which is generated from the deprotonation of sinomenine (1) using potassium carbonate in a solvent of N,N-dimethyl formamide, with 4-methylcarboranyl-n-butyl iodide, (2) forms methylcarboranyl-n-butyl sinomenine (3) in 54.3% yield as a new product. This new compound was characterized by 1H, 13C, and 11B NMR spectroscopy, FT-IR spectroscopy, and elemental analyses to confirm its molecular composition. In addition to molecular docking interactions with MMPs, the in vitro killing effects of 3, along with its toxicity measurements, exhibited its potential to be the new drug delivery agent for boron neutron capture synovectomy (BNCS) and boron neutron capture therapy (BNCT) for the treatment of rheumatoid arthritis (RA) and cancers in the presence of slow neutrons, respectively.

Structural basis for the catalytic mechanism and α-ketoglutarate cooperativity of glutamate dehydrogenase.

Glutamate dehydrogenase (GDH) is a key enzyme connecting carbon and nitrogen metabolism in all living organisms. Despite extensive studies on GDHs from both prokaryotic and eukaryotic organisms in the last 40 years, the structural basis of the catalytic features of this enzyme remains incomplete. This study reports the structural basis of the GDH catalytic mechanism and allosteric behavior. We determined the first high-resolution crystal structures of glutamate dehydrogenase from the fungus Aspergillus niger (AnGDH), a unique NADP+-dependent allosteric enzyme that is forward-inhibited by the formation of mixed disulfide. We determined the structures of the active enzyme in its apo form and in binary/ternary complexes with bound substrate (α-ketoglutarate), inhibitor (isophthalate), coenzyme (NADPH), or two reaction intermediates (α-iminoglutarate and 2-amino-2-hydroxyglutarate). The structure of the forward-inhibited enzyme (fiAnGDH) was also determined. The hexameric AnGDH had three open subunits at one side and three partially closed protomers at the other, a configuration not previously reported. The AnGDH hexamers having subunits with different conformations indicated that its α-ketoglutarate-dependent homotropic cooperativity follows the Monod-Wyman-Changeux (MWC) model. Moreover, the position of the water attached to Asp-154 and Gly-153 defined the previously unresolved ammonium ion-binding pocket, and the binding site for the 2'-phosphate group of the coenzyme was also better defined by our structural data. Additional structural and mutagenesis experiments identified the residues essential for coenzyme recognition. This study reveals the structural features responsible for positioning α-ketoglutarate, NADPH, ammonium ion, and the reaction intermediates in the GDH active site.

Characterization of 4-guanidinobutyrase from Aspergillus niger.

Arginase is the only fungal ureohydrolase that is well documented in the literature. More recently, a novel route for agmatine catabolism in Aspergillus niger involving another ureohydrolase, 4-guanidinobutyrase (GBase), was reported. We present here a detailed characterization of A. niger GBase - the first fungal (and eukaryotic) enzyme to be studied in detail. A. niger GBase is a homohexamer with a native molecular weight of 336 kDa and an optimal pH of 7.5. Unlike arginase, the Mn2+ enzyme from the same fungus, purified GBase protein is associated with Zn2+ ions. A sensitive fluorescence assay was used to determine its kinetic parameters. GBase acted 25 times more efficiently on 4-guanidinobutyrate (GB) than 3-guanidinopropionic acid (GP). The Km for GB was 2.7±0.4 mM, whereas for GP it was 53.7±0.8 mM. While GB was an efficient nitrogen source, A. niger grew very poorly on GP. Constitutive expression of GBase favoured fungal growth on GP, indicating that GP catabolism is limited by intracellular GBase levels in A. niger. The absence of a specific GPase and the inability of GP to induce GBase expression confine the fungal growth on GP. That GP is a poor substrate for GBase and a very poor nitrogen source for A. niger offers an opportunity to select GBase specificity mutations. Further, it is now possible to compare two distinct ureohydrolases, namely arginase and GBase, from the same organism.

The Transition from Metal-Based to Metal-Free Contrast Agents for T1 Magnetic Resonance Imaging Enhancement.

Magnetic resonance imaging (MRI) has received significant attention as the noninvasive diagnostic technique for complex diseases. Image-guided therapeutic strategy for diseases such as cancer has also been at the front line of biomedical research, thanks to the innovative MRI, enhanced by the prior delivery of contrast agents (CAs) into patients' bodies through injection. These CAs have contributed a great deal to the clinical utility of MRI but have been based on metal-containing compounds such as gadolinium, manganese, and iron oxide. Some of these CAs have led to cytotoxicities such as the incurable Nephrogenic Systemic Fibrosis (NSF), resulting in their removal from the market. On the other hand, CAs based on organic nitroxide radicals, by virtue of their structural composition, are metal free and without the aforementioned drawbacks. They also have improved biocompatibility, ease of functionalization, and long blood circulation times, and have been proven to offer tissue contrast enhancement with longitudinal relaxivities comparable with those for the metal-containing CAs. Thus, this Review highlights the recent progress in metal-based CAs and their shortcomings. In addition, the remarkable goals achieved by the organic nitroxide radical CAs in the enhancement of MR images have also been discussed extensively. The focal point of this Review is to emphasize or demonstrate the crucial need for transition into the use of organic nitroxide radicals-metal-free CAs-as against the metal-containing CAs, with the aim of achieving safer application of MRI for early disease diagnosis and image-guided therapy.

Visceral leishmaniasis: A novel nuclear envelope protein 'nucleoporins-93 (NUP-93)' from Leishmania donovani prompts macrophage signaling for T-cell activation towards host protective immune response.

The shift of macrophage and T-cell repertoires towards proinflammatory cytokine signalling ensures the generation of host-protective machinery that is otherwise compromised in cases of the intracellular Leishmania parasite. Different groups have attempted to restore host protective immunity. These vaccine candidates showed good responses and protective effects in murine models, but they generally failed during human trials. In the present study, we evaluated the effect of 97 kDa recombinant nucleoporin-93 of Leishmania donovani (rLd-NUP93) on mononuclear cells in healthy and treated visceral leishmaniasis (VL) patients and on THP-1 cell lines. rLd-NUP93 stimulation increased the expression of the early lymphocyte activation marker CD69 on CD4+ and CD8+ T cells. The expression of the host protective pro-inflammatory cytokines IFN-γ, IL-12 and TNF-α was increased, with a corresponding down-regulation of IL-10 and TGF-ß upon rLd-NUP93 stimulation. This immune polarization resulted in the up-regulation of NF-κB p50 with scant expression of SMAD-4. Augmenting lymphocyte proliferation upon priming with rLd-NUP93 ensured its potential for activation and generation of strong T-cell mediated immune responses. This stimulation extended the leishmanicidal activity of macrophages by releasing high amounts of reactive oxygen species (ROS). Further, the leishmanicidal activity of macrophages was intensified by the elevated production of nitric oxide (NO). The fact that this antigen was earlier reported in circulating immune complexes of VL patients highlights its antigenic importance. In addition, in silico analysis suggested the presence of MHC class I and II-restricted epitopes that proficiently trigger CD8+ and CD4+ T-cells, respectively. This study reported that rLd-NUP93 was an effective immunoprophylactic agent that can be explored in future vaccine design.

2-Oxoglutarate cooperativity and biphasic ammonium saturation of Aspergillus niger NADP-glutamate dehydrogenase are structurally coupled.

NADP-glutamate dehydrogenase from Aspergillus niger (AnGDH) exhibits sigmoidal 2-oxoglutarate saturation. Despite sharing 88% amino acid identity, the homologous enzyme from Aspergillus terreus (AtGDH) shows hyperbolic 2-oxoglutarate saturation. In order to address the structural origins of this phenomenon, six AnGDH-AtGDH chimeras were constructed and characterized. The C-terminal sequence (residues 315-460, named the D-segment) was implicated in the AnGDH cooperativity. The D-segment residues largely contribute to the monomer-monomer interface of each trimer in the native hexamer and are far removed from the enzyme active site. The D-segment appears to be a part of the allosteric network responsible for 2-oxoglutarate homotropic interactions in AnGDH. AnGDH and its C415S mutant, but not AtGDH, also showed atypical, biphasic ammonium saturation, particularly at sub-saturating 2-oxoglutarate concentrations. We found that the sigmoidal 2-oxoglutarate saturation and the biphasic ammonium response are tightly coupled; the analysis of AnGDH-AtGDH chimeras ascribes the two features to the AnGDH D-segment. The two non-Michaelis-Menten substrate saturations of AnGDH were influenced by ionic strength. Increase in ionic strength reduced the nH of 2-oxoglutarate saturation as well as abolished the biphasic response, suggesting that polar/ionic interactions determine the allosteric, inter-subunit communications. The biochemical analysis in the context of available structural data implicates the D-segment of AnGDH in the allosteric feature of this enzyme. The coupling of sigmoidal 2-oxoglutarate saturation and the biphasic ammonium response could possibly confer growth advantage to A. niger experiencing carbon and/or nitrogen limitation.

Comparing phase and electrographic flow mapping for persistent atrial fibrillation.

BACKGROUND: An increasing number of methods are being used to map atrial fibrillation (AF), yet the sensitivity of identifying potential localized AF sources of these novel methods are unclear. Here, we report a comparison of two approaches to map AF based upon (1) electrographic flow mapping and (2) phase mapping in a multicenter registry of patients in whom ablation terminated persistent AF. METHODS: Fifty-three consecutive patients with persistent AF in whom ablation terminated AF in an international multicenter registry were enrolled. Electrographic flow mapping (EGF) and phase mapping were applied to the multipolar simultaneous electrograms recorded from a 64-pole basket catheter in the chamber (left vs right atrium) where AF termination occurred. We analyzed if the mapping methods were able to detect localized sources at the AF termination site. We also analyzed global results of mapping AF for each method, patterns of activation of localized sources. RESULTS: Patients were 64.3 ± 9.4 years old and 69.8% were male. EGF and phase mapping identified localized sources at AF termination sites in 81% and 83% of the patients, respectively. Methods were complementary and in only n = 2 (3.7%) neither method identified a source. Globally, EGF identified more localized sources than phase mapping (5.3 ± 2.8 vs 1.8 ± 0.5, P < 0.001), with a higher prevalence of focal (compared to rotational) activation pattern (49% vs 2%, P < 0.01). CONCLUSIONS: EGF is a novel vectorial-based AF mapping method, which can detect sites of AF termination, agreeing with, and complementary to, an alternative AF mapping method using phase analysis.

Synthesis and in vitro anti-tumor activity of carboranyl levodopa.

Reactions of closo-1-Me-2-Iodobutyl-1,2-closo-dicarborane, 1-Me-2-I(CH2)4-C2B10H10, with l-dopa methyl ester can produce carboranyl l-dopa methyl esters in 54% yield in the presence of sodium hydroxide. The appended closo-carboranes can be decapitated with sodium hydroxide in a mixed solvent of ethanol and deionized water to produce highly water-soluble carboranyl levodopa in 64% yield. All the new compounds were characterized by 1H, 13C, 11B NMR, FT-IR spectroscopy and elemental analysis. The highly water soluble carboranyl levodopa 4 shows promising efficacy of anti-tumors in vitro in the presence of slow neutron beams.