Oligoribonucleotides containing an aminoalkyl group at the N(4) atom of cytosine as precursors of new reagents for site-specific modifications of biopolymers

A solid-phase H-phosphonate procedure was developed for the synthesis of oligoribonucleotides containing aliphatic amino linkers with different lengths at the N(4) atom of cytosine. The hybridization properties of modified oligoribonucleotides were studied. Thermal stability of the RNA—RNA* and DNA—RNA* duplexes depends on the position of modified cytosine in the chain and the type of the duplex.     

An Aldehyde Responsive,Cleavable Linker for Glucose Responsive Insulins

A glucose responsive insulin (GRI) that responds to changes in blood glucose concentrations has remained an elusive goal. Here we describe the development of glucose cleavable linkers based on hydrazone and thiazolidine structures. We developed linkers with low levels of spontaneous hydrolysis but increased level of hydrolysis with rising concentrations of glucose, which demonstrated their glucose responsiveness in vitro. Lipidated hydrazones and thiazolidines were conjugated to the LysB29 side-chain of HI by pH-controlled acylations providing GRIs with glucose responsiveness confirmed in vitro for thiazolidines. Clamp studies showed increased glucose infusion at hyperglycemic conditions for one GRI indicative of a true glucose response. The glucose responsive cleavable linker in these GRIs allow changes in glucose levels to drive the release of active insulin from a circulating depot. We have demonstrated an unprecedented, chemically responsive linker concept for biopharmaceuticals.     

Cytotoxicity of Amino-BODIPY Modulated via Conjugation with 2-Phenyl-3-Hydroxy-4(1H)-Quinolinones

The combination of cytotoxic amino-BODIPY dye and 2-phenyl-3-hydroxy-4(1H)-quinolinone (3-HQ) derivatives into one molecule gave rise to selective activity against lymphoblastic or myeloid leukemia and the simultaneous disappearance of the cytotoxicity against normal cells. Both species′ conjugation can be realized via a disulfide linker cleavable in the presence of glutathione characteristic for cancer cells. The cleavage liberating the free amino-BODIPY dye and 3-HQ derivative can be monitored by ratiometric fluorescence or by the OFF-ON effect of the amino-BODIPY dye. A similar cytotoxic activity is observed when the amino-BODIPY dye and 3-HQ derivative are connected through a non-cleavable maleimide linker. The work reports the synthesis of several conjugates, the study of their cleavage inside cells, and cytotoxic screening.     

Theoretical investigation of nonlinear optical behavior for rod and T-Shaped phenothiazine based D-π-A organic compounds and their derivatives

The exploration of novel materials with excellent nonlinear optical (NLO) features is an area of frontline investigation for scientific community from technological point of view. This study reports the novel phenothiazine-based rod-shaped and T-shaped NLO molecules which are quantum chemically designed from synthesized compounds: rod-shaped (CFA and CBA) and T-shaped (CTA, CCA and CPA). Structural tailoring was performed on D-π-π-A centered CPA chromophore and the effect of various π-spacers, as well as solvents on NLO response properties is investigated. Density functional theory (DFT) along with time dependent DFT (TDDFT) calculations have been executed at B3LYP/6-311G(d,p) functional to examine entire analysis. Results showed a smaller energy gap in structurally modified compounds as compared to reference CPA. Global reactivity parameters analysis revealed smaller hardness and larger softness values in T-shaped compounds. UV–Vis analysis of investigated molecules displayed a red shift in absorption maximum value as compared to CPA. Natural bond orbital (NBO) and frontier molecular orbital (FMO) analysis revealed the stability and intra-molecular electron transferring (ICT) process in investigated molecules. ICT showed the effective charge shift from donor to acceptor via π-spacers. Overall, promising NLO response exists in gas phase and different solvents (acetonitrile, ethyl alcohol and water). Interestingly, proposed molecule CPP presented a maximum value of linear polarizability < α > as 1518.23 a.u and first hyperpolarizability (β_tot) as 755322.39 a.u in acetonitrile solvent. In short, entitled chromophores exhibited excellent NLO properties due to their lower charge transport resistance. This NLO study may open a new topic for researchers to discover novel NLO for hi-tech submissions of modern era.     

A Microgel Construction Kit for Bioorthogonal Encapsulation and pH‐Controlled Release of Living Cells

pH‐Cleavable cell‐laden microgels with excellent long‐term viabilities were fabricated by combining bioorthogonal strain‐promoted azide–alkyne cycloaddition (SPAAC) and droplet‐based microfluidics. Poly(ethylene glycol)dicyclooctyne and dendritic poly(glycerol azide) served as bioinert hydrogel precursors. Azide conjugation was performed using different substituted acid‐labile benzacetal linkers that allowed precise control of the microgel degradation kinetics in the interesting pH range between 4.5 and 7.4. By this means, a pH‐controlled release of the encapsulated cells was achieved upon demand with no effect on cell viability and spreading. As a result, the microgel particles can be used for temporary cell encapsulation, allowing the cells to be studied and manipulated during the encapsulation and then be isolated and harvested by decomposition of the microgel scaffolds.     

In‐ and Out‐of‐Cavity Interactions by Modulating the Size of Ruthenium Metallarectangles

Cationic (arene)ruthenium‐based tetranuclear complexes of the general formula [Ru₄(η⁶‐p‐cymene)₄(μ‐N∩N)₂(μ‐OO∩OO)₂]⁴⁺ were obtained from the dinuclear (arene)ruthenium complexes [Ru₂(η⁶‐p‐cymene)₂(μ‐OO∩OO)₂Cl₂] (p‐cymene=1‐methyl‐4‐(1‐methylethyl)benzene, OO∩OO=5,8‐dihydroxy‐1,4‐naphthoquinonato(2?), 9,10‐dihydroxy‐1,4‐anthraquinonato(2?), or 6,11‐dihydroxynaphthacene‐5,12‐dionato(2?)) by reaction with pyrazine or bipyridine linkers (N∩N=pyrazine, 4,4′‐bipyridine, 4,4′‐[(1E)‐ethene‐1,2‐diyl]bis[pyridine]) in the presence of silver trifluoromethanesulfonate (CF₃SO₃Ag) (Scheme). All complexes 4 – 12 were isolated in good yield as CF₃SO salts, and characterized by NMR and IR spectroscopy. The host–guest properties of the metallarectangles incorporating 4,4′‐bipyridine and (4,4′‐[(1E)‐ethene‐1,2‐diyl]bis[pyridine] linkers were studied in solution by means of multiple NMR experiments (1D, ROESY, and DOSY). The largest metallarectangles 10 – 12 incorporating (4,4′‐[(1E)‐ethene‐1,2‐diyl]bis[pyridine] linkers are able to host an anthracene, pyrene, perylene, or coronene molecule in their cavity, while the medium‐size metallarectangles 7 – 9 incorporating 4,4′‐bipyridine linkers are only able to encapsulate anthracene. However, out‐of‐cavity interactions are observed between these 4,4′‐bipyridine‐containing rectangles and pyrene, perylene, or coronene. In contrast, the small pyrazine‐containing metallarectangles 4 – 6 show no interaction in solution with this series of planar aromatic molecules.     

A one‐dimensional cadmium metal–organic chain based on a [Cd4(COO)4] secondary building unit and a flexible dicarboxylic acid ligand

An infinite one‐dimensional cadmium metal–organic chain, namely catena‐poly[aquabis(μ₃‐2,2′‐{[1,2‐phenylenebis(methylene)]bis(sulfanediyl)}dibenzoato)dicadmium(II)], [Cd₂(C₂₂H₁₆O₄S₂)₂(H₂O)]_n, was synthesized by solvothermal reaction of Cd(NO₃)₂·4H₂O and 2,2′‐{[1,2‐phenylenebis(methylene)]bis(sulfanediyl)}dibenzoic acid (H₂L). The Cd^II centres have six‐coordinate CdS₂O₄ and CdSO₅ geometries. Due to the flexible –CH₂–S– arms, the L²⁻ ligand adopts both syn and anti conformations. Four Cd^II cations are linked by two syn L²⁻ ligands to form a centrosymmetric planar tetranuclear Cd^II core, which is further extended through bonding to the anti L²⁻ ligands to form a one‐dimensional metal–organic chain. Adjacent one‐dimensional chains are connected by C—H...π interactions and nonclassical C—H...O hydrogen bonds to form the resultant three‐dimensional supramolecular framework.     

Double-stranded ladderphanes with C2-symmetric planar chiral ferrocene linkers

Eight ladderphanes with C₂-symmetric planar chiral ferrocene linkers are synthesized by ring opening metathesis polymerization of bisnorbornene monomers using Grubbs-I catalyst. The aminobenzoate in both monomers and polymers shows absorption maximum around 320 nm. Both monomers and polymers are Circular dichroism (CD) active. Little enhancements of CD profiles around 320 nm are observed for ladderphanes having chiral chloro- or phenyl-substituted ferrocene linkers. However, ladderphanes with a phenyl substituent on the cyclopendienyl ring exhibits enhancement of CD curves aound 240–300 nm. The congested phenyl moieties in adjacent linkers in this polymer might be well oriented such that interactions between these aromatic substituents on different monomeric units might provoke the enhancement of the CD curves in this region. When the methyl-substituted cyclopendienyl ligand is used for chiral ferrocene linkers, the ladderphanes exhibit two-fold enhancement of CD spectrum around 320 nm. This enhancement is further increased when the cyclopentadienyl ligand contains an additional phenyl substituent, owing to exciton coupling between aminobenzoate moieties in adjacent monomeric units. Moreover, the intensity of the CD curves in the region of 240–300 nm is significantly increased. These results suggest that the later polymer may adopt a posible helical structure. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2999–3010     

Synthesis of novel rigid-rod and tripodal azulene chromophores

Two novel azulene chromophores 1 and 2 were synthesized to study dynamics of ultrafast electron injection at the interface of TiO₂ semiconductor nanoparticles. Fluorescence quenching was observed upon binding.     

Metal-Mediated Directional Capping of Rod-Packing Metal–Organic Frameworks

Two new rod-packing metal–organic frameworks (RPMOF) are constructed by regulating the in situ formation of the capping agent. In CPM-s7, carboxylate linkers extend 1D manganese-oxide chains in four additional directions, forming 3D RPMOF. The substitution of Mn²⁺ with a stronger Lewis acidic Co²⁺, leads to an acceleration of the hydrolysis-prone sulfonate linker, resulting in presence of sulfate ions to reduce two out of the four carboxylate-extending directions, and thus forming a new 2D rod-packing CPM-s8. Density functional theory calculations and magnetization measurements reveal ferrimagnetic ordering of CPM-s8, signifying the potential of exploring 2D RPMOF for effective low-dimensional magnetic materials.