Handan Akpinar

Sensing of proteins in human serum using conjugates of nanoparticles and green fluorescent protein

There is a direct correlation between protein levels and disease states in human serum making it an attractive target for sensors and diagnostics. However this is made challenging because serum features more than 20,000 proteins with an overall protein content of greater than 1 mM. Here we report a hybrid synthetic-biomolecule based sensor that uses green fluorescent protein-nanoparticle arrays to detect proteins at biorelevant concentrations in both buffer and human serum. Distinct and reproducible fluorescence response patterns were obtained from five serum proteins (human serum albumin, immunoglobulin G, transferrin, fibrinogen and α-antitrypsin) in buffer and when spiked into human serum. Using linear discriminant analysis we identified these proteins with an identification accuracy of 100% in buffer and 97% in human serum. The arrays were also able to discriminate between different concentrations of the same protein as well as a mixture of different proteins in human serum.There is a direct correlation between protein levels and disease states in human serum, which makes it an attractive target for sensors and diagnostics. However, this is challenging because serum features more than 20,000 proteins, with an overall protein content greater than 1 mM. Here we report a sensor based on a hybrid synthetic-biomolecule that uses arrays of green fluorescent protein and nanoparticles to detect proteins at biorelevant concentrations in both buffer and human serum. Distinct and reproducible fluorescence-response patterns were obtained from five serum proteins (human serum albumin, immunoglobulin G, transferrin, fibrinogen and a-antitrypsin), both in buffer and when spiked into human serum. Using linear discriminant analysis we identified these proteins with an identification accuracy of 100% in buffer and 97% in human serum. The arrays were also able to discriminate between different concentrations of the same protein, as well as a mixture of different proteins in human serum.

A Cobalt Pyrenylnitronylnitroxide Single‐Chain Magnet with High Coercivity and Record Blocking Temperature

Coordination of a [Co(hfac)2] moiety (hfac = hexafluoroacetylacetonate) with a nitronylnitroxide radical linked to bulky, rigid pyrene (PyrNN) gives a helical 1:1 chain complex, in which both oxygen atoms of the radical NO(·) groups are bonded to Co(II) ions with strong antiferromagnetic exchange. The complex shows single-chain magnet (SCM) behavior with frequency-dependent magnetic susceptibility, field-cooled and zero-field-cooled susceptibility divergence with a high blocking temperature of around 14 K (a record among SCMs), and hysteresis with a very large coercivity of 32 kOe at 8 K. The magnetic behavior is partly related to good chain isolation induced by the large pyrene units. Two magnetic relaxation processes have been observed, a slower one attributable to longer, and a faster one attributable to short chains. No evidence of magnetic ordering has been found.

Radicals organized by disk shaped aromatics – polymorphism and co-crystals that tune inter-electron exchange

Polymorphisms effect on intermolecular packing is a critical consideration for organic magnetic materials. Magnetostructural studies of pyrene-1-yl (Pyr) bearing nitronylnitroxide (NN) and iminoylnitroxide (IN) radicals found that PyrNN gives two allotropes: one has spin-paired dyads with ΔE = J/k ≈–178 K, and one is half spin-paired with ΔE = J/k ≈ −102 K, and half paramagnetic. PyrIN also gives two allotropes, one an anti conformation that is spin paired with ΔE = J/k = −410 K, and one a paramagnetic system having a syn conformation. PyrNN co-crystallizes with C6F6 in 2 : 1 ratio with a methyl to nitroxide contact network exhibiting low dimensional 1-D or 2-D antiferromagnetic exchange.

A co-crystal of 2-(1′-pyrenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl with octafluoronaphthalene

2-(1′-Pyrenyl)nitronylnitroxide (PyrNN) forms a 2 : 1 : 2 co-crystal with octafluoronaphthalene (OFN) and entrained solvent dichloromethane (DCM), in which the radical is “shepherded” into forming chains of radical–radical contacts on the peripheries of (PyrNN–OFN–PyrNN)n π-stacks, giving weak, low dimensional inter-radical antiferromagnetic exchange interactions.

Two co-crystalline M(hfac)2(IPhIN)2·M(hfac)2 (M = Mn, Co) compounds with a bis(iminoylnitroxide) biradical: structure and magnetism

1-Iodo-3,5-bis(4′,4′,5′,5′-tetramethyl-4′,5′-dihydro-1H-imidazole-1′-oxyl)benzene (IPhIN = L) forms co-crystalline [M(hfac)2(IPhIN)2]·[M(hfac)2] coordination complexes (M = Mn, Co) with [Mn(hfac)2] and [Co(hfac)2]. In each system only one of the iminoylnitroxide radical moieties is coordinated as part of the [M(hfac)2(IPhIN)2] structural units; the metal ions do not coordinate the radical nitrogen atoms, but rather the nitroxide oxygen to form a cis NO–M–ON grouping in a hexacoordinate ligand sphere. Solvate water molecules in the lattice provide an important driving force for assembly of the co-crystal structures in the cobalt(II) derivative; an additional factor is the formation of halogen bonds between hfac CF3 groups and the IPhIN iodine atom. The paramagnetic susceptibility (χM) versus temperature (T) measurements showed antiferromagnetic exchange downturns at lower temperature. Based on the crystal structures of the complexes, the χMT versus T data were modelled using a paramagnetic contribution from the [M(hfac)2] fragment, an exchange interaction J1 within the L–M–L fragment, plus an intramolecular radical–radical interaction J2 within the IPhIN biradical unit. For the Mn(II) complex, a good fit was obtained for gMn = 2.14(1), grad = 2.0 (fixed), J1 = −311(9) cm−1 and J2 = 11.1(7) cm−1. A reasonable fit for the cobalt compound was obtained for gCo = 2.72(1), grad = 2.0 (fixed), J1 = −400(5) cm−1, J2 = 28.3(3) cm−1 with a generalized zero field splitting parameter D = 64(2) cm−1.

2-(9,10-Anthraquinon-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl: polymorphism in a conjugated anthraquinone-substituted nitronylnitroxide

Two polymorphs of an anthraquinone-nitronylnitroxide radical, AntQNN, were isolated, both with antiferromagnetic (AFM) exchange attributed to chain-type inter-radical contacts: one with J1D/k ≈ -3 K, and one with J1D/k ≈ -17 K.

Organizing a bis(iminoylnitroxide) diradical into antiferromagnetically coupled chains by co-crystallization with dichloromethane

1,3-Bis(4′,4′,5′,5′-tetramethyl-4′,5′-dihydro-1′H-imidazol-2′-yl-1′-oxyl)-5-iodobenzene (IPhIN2) forms a co-crystal with dichloromethane (CH2Cl2) and some water, with columnar π-stacking of radical N–O moieties organized into antiferromagnetically exchange-coupled 1-D chains.