Longitudinal brain imaging of five malignant glioma patients treated with bevacizumab using susceptibility-weighted magnetic resonance imaging at 7 T

Malignant glioma is a rare tumor type characterized by prominent vascular proliferation. Antiangiogenic therapy with the monoclonal antibody bevacizumab is considered as a promising therapeutic strategy, although the effect on tumor vascularization is unclear. High-field susceptibility-weighted imaging (SWI) visualizes the microvasculature and may contribute to the investigation of antiangiogenic therapy responses in gliomas. We prospectively studied five adult malignant glioma patients treated with bevacizumab-containing regimens. In each patient, we performed three 7-T SWI and T1-weighted imaging investigations (baseline and 2 and 4 weeks after the start of bevacizumab treatment). In addition, we imaged a postmortem brain of a patient with glioblastoma using 7-T SWI and performed detailed histopathological analysis. We observed almost total resolution of brain edema in three of five patients after initiation of bevacizumab therapy. In one case with rapid increase of the lesion size despite bevacizumab therapy, SWI showed progressive increase of irregular hypointense structures, most likely corresponding to increasing amounts of pathological microvasculature. In one case with progressive neurological decline, 7-T images showed multiple intratumoral microhemorrhages after the first bevacizumab application. Correlation of postmortem neuroimaging with histopathology confirmed that SWI-positive structures correspond to tumor vasculature. The experience from our case series indicates that longitudinal 7-T SWI seems to be an appropriate method for investigation of changes in brain tumor vascularization over time under antiangiogenic therapy.     

Porous interpenetrated zirconium-organic frameworks (PIZOFs): a chemically versatile family of metal-organic frameworks

We present the synthesis and characterization of porous interpenetrated zirconium-organic frameworks (PIZOFs), a new family of metal-organic frameworks obtained from ZrCl(4) and the rodlike dicarboxylic acids HO(2)C[PE-P(R(1),R(2))-EP]CO(2) H that consist of alternating phenylene (P) and ethynylene (E) units. The substituents R(1),R(2) were broadly varied (alkyl, O-alkyl, oligo(ethylene glycol)), including postsynthetically addressable substituents (amino, alkyne, furan). The PIZOF structure is highly tolerant towards the variation of R(1) and R(2). This together with the modular synthesis of the diacids offers a facile tuning of the chemical environment within the pores. The PIZOF structure was solved from single-crystal X-ray diffraction analysis. The PIZOFs are stable under ambient conditions. PIZOF-2, the PIZOF prepared from HO(2)C[PE-P(OMe,OMe)-EP]CO(2)H, served as a prototype to determine thermal stability and porosity. It is stable up to 325 °C in air as determined by using thermogravimetry and powder X-ray diffraction. Argon sorption isotherms on PIZOF-2 revealed a Brunauer-Emmett-Teller (BET) surface area of 1250 m(2) g(-1) and a total pore volume of 0.68 cm(3) g(-1).     

Modulated synthesis of Zr-based metal-organic frameworks: from nano to single crystals

We present an investigation on the influence of benzoic acid, acetic acid, and water on the syntheses of the Zr-based metal-organic frameworks Zr-bdc (UiO-66), Zr-bdc-NH(2) (UiO-66-NH(2)), Zr-bpdc (UiO-67), and Zr-tpdc-NH(2) (UiO-68-NH(2)) (H(2) bdc: terephthalic acid, H(2) bpdc: biphenyl-4,4'-dicarboxylic acid, H(2) tpdc: terphenyl-4,4'-dicarboxylic acid). By varying the amount of benzoic or acetic acid, the synthesis of Zr-bdc can be modulated. With increasing concentration of the modulator, the products change from intergrown to individual crystals, the size of which can be tuned. Addition of benzoic acid also affects the size and morphology of Zr-bpdc and, additionally, makes the synthesis of Zr-bpdc highly reproducible. The control of crystal and particle size is proven by powder XRD, SEM and dynamic light scattering (DLS) measurements. Thermogravimetric analysis (TGA) and Ar sorption experiments show that the materials from modulated syntheses can be activated and that they exhibit high specific surface areas. Water proved to be essential for the formation of well-ordered Zr-bdc-NH(2) . Zr-tpdc-NH(2), a material with a structure analogous to that of Zr-bdc and Zr-bpdc, but with the longer, functionalized linker 2'-amino-1,1':4',1'-terphenyl-4,4'-dicarboxylic acid, was obtained as single crystals. This allowed the first single-crystal structural analysis of a Zr-based metal-organic framework.     

A Chemiluminescent Metal–Organic Framework

The synthesis and characterization of a chemiluminescent metal–organic framework with high porosity is reported. It consists of Zr₆O₆(OH)₄ nodes connected by 4,4′-(anthracene-9,10-diyl)dibenzoate as the linker and luminophore. It shows the topology known for UiO-66 and is therefore denoted PAP-UiO. The MOF was not only obtained as bulk material but also as a thin film. Exposure of PAP-UiO as bulk or film to a mixture of bis-(2,4,6-trichlorophenyl) oxalate, hydrogen peroxide, and sodium salicylate in a mixture of dimethyl and dibutyl phthalate evoked strong and long lasting chemiluminescence of the PAP-UiO crystals. Time dependent fluorescence spectroscopy on bulk PAP-UiO and, for comparison, on dimethyl 4,4′-(anthracene-9,10-diyl)dibenzoate provided evidence that the chemiluminescence originates from luminophores being part of the PAP-UiO, including the luminophores inside the crystals.     

Direct conversion of EPR dipolar time evolution data to distance distributions

Shallow electron spin echo envelope modulations due to dipole-dipole couplings between electron spins provide information on the radial distribution function of the spins in disordered systems while angular correlations between spin pairs are negligible. Under these conditions and in the absence of orientational selection, the dipolar time evolution data can be quantitatively simulated for arbitrary radial distribution functions by shell factorization, i.e., by performing the orientational average separately for thin spherical shells and multiplying the signals of all the shells. For distances below 5 nm, a linear superposition of the signals of the shells is sufficient. The dipolar time evolution data can be separated into this linear contribution and a nonlinear background. The linear contribution can then be converted directly to a radial distribution function. For a series of shape-persistent and flexible biradicals with end-to-end distances between 2 and 5 nm, shell factorization and direct conversion of the data are in good agreement with each other and with force-field computations of the end-to-end distances. The neglect of orientation selection does not cause significant distortions of the determined distance distributions.     

Über einen Mikro-Kühltisch und seine Anwendung

Zusammenfassung Auf Grund der Erfahrungen mit dem Mikro-Heiztisch wurde ein Mikro-Kühltisch hergestellt, der in seiner Handhabung einfach und jederzeit gebrauchsfähig ist. Die Kühlung erfolgt durch Verdampfen von flüssiger Kohlensäure. Eine daneben eingebaute elektrische Heizung ermöglicht es, auch den Bereich der Raumtemperatur nach beiden Richtungen mit beliebiger Geschwindigkeit zu durchschreiten. Der Apparat umfaßt einen Temperaturbereich von –55° bis +80°.Auf diesem Kühltisch lassen sich bei organischen und anorganischen Stoffen und Stoffgemischen alle Erscheinungen, die sich bei Temperaturänderungen bei und unterhalb Raumtemperatur abspielen, in analog einfacher Weise beobachten und leiten wie die entsprechenden Vorgänge oberhalb Raumtemperatur am Heiztisch. An einer Reihe von Beispielen werden folgende Untersuchungen beschrieben: Schmelz- und Erstarrungspunkte, eutektische bzw. kryohydratische Temperaturen, Polymorphieund Isomorphiebeziehungen, Nachweis von Molekülverbindungen, Übergangspunkte bei Hydraten, Auftreten stabilisierter Zwischenphasen, eutektische und quasi-eutektische Kristallisation, normale und anormale Abscheidungsfolge bei Unterkühlung und die damit zusammenhängende Erscheinung der Hofbildung.

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Summary On the basis of experience with the micro hot stage, a micro-cooling stage was constructed, which is simple in operation and ready for use at all times. The cooling is secured through vaporization of liquid carbon dioxide. A neighboring built-in electrical heater makes it possible also to pass through the region of room temperature in either direction with any desired speed. The apparatus has a temperature range from –55° to + 80°.On this cooling stage organic and inorganic materials and mixtures show all the phenomena, which occur at temperature changes at and below room temperature, and these may be observed in analogously simple fashion and controlled as in the case of the corresponding processes occurring at temperatures above room temperature on the hot stage. The following studies were described from a series of investigations: melting and solidification points; eutectic and cryohydric temperatures; polymorphic and isomeric relationships; detection of molecular compounds; transition points of hydrates; appearance of stable intermediate phases; eutectic and quasi-eutectic crystallization; normal and abnormal precipitation succession on supercooling and the related phenomena of halo formation.

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Résumé Sur la base des expériences avec la micro-table chauffante, on a préparé une micro-table réfrigérante, de manipulation simple et toujours prète pour l'emploi. Le refroidissement s'obtient en évaporant de l'anhydride carbonique liquide. Un chauffage électrique installé à côté permet de passer par la température ordinaire, dans les deux sens et avec une vitesse quelconque. L'appareil embrasse un domaine de température de –55° à +80°. A l'aide de cette table réfrigérante, on peut observer, dans les corps organiques et minéraux dans les mélanges, tous les phénomènes qui se produisent par changement de température à l'ambiante ou au-dessous. On peut diriger d'une manière simple et analogue à ce qui se passe sur la table chauffante, au-dessus de la température ordinaire, les processus correspondants. On décrit à l'aide de quelques exemples les expériences suivantes: points de fusion et de solidification, eutectiques ou températures cryohydratiques, relations de polymorphisme et d'isomorphisme, recherche des combinaisons moléculaires, point de transformation chez les hydrates, apparition de phases intermédiaires stables, cristallisation eutectique et quasi-eutectique suite de dépôts normaux et anormaux par sous-refroidissement et les phénomènes de halo qui en résultent.

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Mit 3 Abbildungen.     

Synthese und Struktur von Komplexen mit Nitridobrücken zwischen Rhenium und Zink

Synthesis and Structure of Complexes with Nitrido Bridges between Rhenium and Zinc The reaction of [ReNCl₂(PMePh)₃] with ZnX₂ (X = Cl, Br) in CH₂Cl₂ yields the tetranuclear complexes [(Me₂PhP)₃X₂Re≡N–ZnX₂]₂. In case of the reaction with ZnBr₂ an exchange of the halogen atoms coordinated to the Re atom occurs. [(Me₂PhP)₃Cl₂Re≡N–ZnCl₂]₂ ( 1 ) crystallizes with one centrosymmetric tetranuclear complex in the triclinic unit cell. [(Me₂PhP)₃Br₂Re≡N–ZnBr₂]₂ ( 2 ) forms triclinic crystals with the composition 2 · 2 CH₂Cl₂. The centrosymmetric tetranuclear complexes exhibit analogous structures. Two complexes [ReNX₂(PMe₂Ph)₃] coordinate with the terminal nitrido ligands the Zn atoms of a central unit XZn(μ-X)₂ZnX. The resulting linear nitrido bridges Re≡N–Zn (Re–N–Zn = 178.4° ( 1 ) und 178.0° ( 2 )) are asymmetric with distances Re–N = 170 pm and Zn–N = 199 pm for 1 , and Re–N = 167 pm as well as Zn–N = 201 pm for 2 . The reaction of [ReNCl₂(PMe₂Ph)₃] with ZnI₂ in CH₂Cl₂ presumably first affords [(Me₂PhP)₃ClIRe≡N–ZnI₂]₂, which, however, in the course of crystallization decomposes to yield [(Me₂PhP)₃ClIRe≡N–ZnI₂(OPMe₂Ph)] ( 3 ). Of the two Cl atoms originally coordinated at the Re atom the one in cis position to the nitrido ligand is substituted by iodine. 3 forms monoclinic crystals with the space group P2₁/n. The distances in the linear nitrido bridge (Re–N–Zn = 171.5°) are Re–N = 167.9 pm and Zn–N = 204.9 pm. By the reaction of [ReNCl₂(PMe₂Ph)₃] with ZnX₂ (X = Cl, I) in THF the dinuclear complexes [(Me₂PhP)₃Cl₂Re≡N–ZnCl₂(THF)] ( 4 ) and [(Me₂PhP)₃ClIRe≡N–ZnI₂(THF)] ( 5 ) are obtained. They crystallize isotypically as 4 · THF or 5 · THF in the triclinic space group P1. Their nitrido bridges have the following parameters: Re–N–Zn = 175.2°, Re–N = 167.7 pm, and Zn–N = 202.1 pm for 4 , resp. Re–N–Zn = 174.7°, Re–N = 168.3 pm, and Zn–N = 201.2 pm for 5 .     

Post‐Synthetic Modification of Zr‐Metal–Organic Frameworks through Cycloaddition Reactions

Cycloaddition reactions are highly attractive for post‐synthetic modification of metal–organic frameworks (MOFs). We report herein on cycloaddition reactions with PIZOF(R¹,R²)s, which are porous interpenetrated Zr‐based MOFs with Zr₆O₄(OH)₄(CO₂)₁₂ as the nodes and the dicarboxylates ^?O₂C[PE‐P(R¹,R²)‐EP]CO₂^? (P: phenylene, E: ethynylene; R¹, R²: side chains at the central phenylene unit) as the linkers. 1,3‐Dipolar cycloaddition between the pendant ethyne moieties of PIZOF(OMe,OCH₂C?CH) and 4‐methylbenzyl azide resulted in 98 % conversion of the ethyne groups. Reactions of PIZOF(OMe,O(CH₂)₃furan) with maleimide, N‐methylmaleimide, and N‐phenylmaleimide converted 98, 99, and 89 % of the furan moieties into the Diels–Alder adducts. However, no reaction occurred with maleic anhydride. High‐resolution ¹H NMR spectra were crucial in determining the conversion and identifying the reaction products. Of all the reagents (NaOD/D₂O, D₂SO₄, Bu₄NF, CsF, CsF/DCl, and KHF₂) tested for the disassembly of the PIZOFs in [D₆]DMSO, the combination of CsF and DCl was found to be the best. The disassembly at room temperature was fast (5–15 min), and after the addition of K₂CO₃ the ¹H NMR data were identical to those of the diacids (=protonated linkers) dissolved in pure DMSO. This allowed for simple structure elucidation through data comparison. CsF/DCl dissolves not only PIZOFs but also the hydrolytically very stable UiO‐66.