Extraction of 2'-O-apiosyl-6'-O-crotonic acid-betanin from the ayrampo seed (Opuntia soehrensii) cuticle and its use as an emitting layer in an organic light-emitting diode.

The molecule 2'-O-apiosyl-6'-O-crotonic acid-betanin (called Achkiy) was obtained after an ecofriendly and low-cost purification process of the extract from the ayrampo seed cuticle. Results from EDS give us an idea of the organic elements present in the ayrampo cuticle layer composed of carbon, oxygen and nitrogen. Further characterization analysis of ayrampo extract by Fourier Transform Infrared Spectrophotometry (FTIR) corroborated the presence of characteristic functional groups corresponding to carboxyl, carbonyls, hydroxyls and secondary amines. On the other hand, we have confirmed by absortion peak the glucose, apiosyl, crotonic acid and betanin at 227 nm, 276 nm, 291 nm and 534 nm bands respectively. Mass Spectrometry (MS) characterization was used finally to identify the electroactive Achkiy molecule. This molecule was tested in an Organic Light Emitting Diode (OLED) achieving a luminance of 4.8 Cd m-2 when bias voltage of 16.5 V and a current of 34.1 mA was applied. In addition, the irradiance generated by the Achkiy layer reaches a value of ≈ 113.3 µW m-2 emitting light with a λ ≈ 390.10 nm. These preliminary results report an interesting molecule extracted from a natural pigment wich emits light in the blue region.

Transverse electronic transport in double-stranded DNA nucleotides.

We calculate the transverse current through double-stranded DNA nucleotides using ab initio techniques in order to establish a protocol to recognize the type and sequence of double-stranded DNA nucleotides. The distinct current-voltage features between nucleotides are used as signatures for their characterization and sequencing. Extended bulk gold electrodes as well as extensions of the DNA backbones are tested as contacts for the electron transport, yielding currents 2 orders of magnitude larger for the former. The addition of Na or H positive counterions improves the signal levels, thus leading to a better discrimination, especially when sodium cations are added.

Molecular biosensor based on a coordinated iron complex.

A sensor model based on the porphyrin nucleus of the soluble guanylate cyclase enzyme is modeled and tested with nitric oxide and carbon monoxide. Molecular oxygen is tested as a possible interferer. Geometries and electronic structures of the model are assessed by density functional theory. Vibrational circular dichroism (VCD), infrared, and Raman spectra are obtained for the iron complexes uncoordinated and coordinated with the gas moieties. The sensor is capable of detecting the ligands to different extents. Carbon monoxide is less detectable than nitric oxide due to the adopted position of the molecule in the sensor; carbon oxide is aligned with the iron atom, while nitric oxide and molecular oxygens bend with an angle detectable by the VCD. It is suggested that pollutants may be detected and measured with the proposed biosensors.

Metal-ion effects on the polarization of metal-bound water and infrared vibrational modes of the coordinated metal center of Mycobacterium tuberculosis pyrazinamidase via quantum mechanical calculations.

Mycobacterium tuberculosis pyrazinamidase (PZAse) is a key enzyme to activate the pro-drug pyrazinamide (PZA). PZAse is a metalloenzyme that coordinates in vitro different divalent metal cofactors in the metal coordination site (MCS). Several metals including Co(2+), Mn(2+), and Zn(2+) are able to reactivate the metal-depleted PZAse in vitro. We use quantum mechanical calculations to investigate the Zn(2+), Fe(2+), and Mn(2+) metal cofactor effects on the local MCS structure, metal-ligand or metal-residue binding energy, and charge distribution. Results suggest that the major metal-dependent changes occur in the metal-ligand binding energy and charge distribution. Zn(2+) shows the highest binding energy to the ligands (residues). In addition, Zn(2+) and Mn(2+) within the PZAse MCS highly polarize the O-H bond of coordinated water molecules in comparison with Fe(2+). This suggests that the coordination of Zn(2+) or Mn(2+) to the PZAse protein facilitates the deprotonation of coordinated water to generate a nucleophile for catalysis as in carboxypeptidase A. Because metal ion binding is relevant to enzymatic reaction, identification of the metal binding event is important. The infrared vibrational mode shift of the C═Nε (His) bond from the M. tuberculosis MCS is the best IR probe to metal complexation.

Computational design of a CNT carrier for a high affinity bispecific anti-HER2 antibody based on trastuzumab and pertuzumab Fabs.

This is a preliminary cross multidisciplinary theoretical-computational approach for the design of a drug delivery system based on immunoconjugated carbon nanotube against HER2- overexpressing cancer cells. This drug delivery system allows the release of an encapsulated cytotoxic cocktail in a controlled manner under pulsed radio frequency (RF) irradiation. Our effort is focused on the computational aided design of a high affinity bispecific anti-HER2 antibody and an opening mechanism of the carbon nanotube (CNT) based cytotoxic carrier for controlling multiple drug release. We study the main interactions between the antibody and the antigen by a computational scanning mutagenesis approach of trastuzumab and pertuzumab fragment antigen binding (Fab) structures in order to enhance their binding affinity. Then, each Fab fragments is joined by a polypeptide linker which should be stable enough to avoid the "open form" of antibody. On the other hand, we also conjugate the engineered antibody to functionalized CNTs (f-CNTs), which encapsulate the inhibitors of the HER2/PI3K/Akt/mTOR signaling pathway. We take advantage of the fact that f-CNT converts the RF radiation absorption into heat release. A pulsed laser at 13.45 MHz increments the temperature around 40 °C for triggering the nano-caps destabilization, which allows the switching of the opening mechanism of the drug carrier. Nano-caps will be a dual pH/temperature responsive in order to take advantage of lysosome characteristic (acidic pH) and heat release from the carrier. Nano-caps are functionalized with organic amide moieties, which hydrolyze quickly at an acidic pH into primary amines, and protonated amines generate repulsion interactions with other charged species, which trigger the cytotoxics release.

Light activation of the isomerization and deprotonation of the protonated Schiff base retinal.

We perform an ab initio analysis of the photoisomerization of the protonated Schiff base of retinal (PSB-retinal) from 11-cis to 11-trans rotating the C10-C11=C12-C13 dihedral angle from 0° (cis) to -180° (trans). We find that the retinal molecule shows the lowest rotational barrier (0.22 eV) when its charge state is zero as compared to the barrier for the protonated molecule which is ∼0.89 eV. We conclude that rotation most likely takes place in the excited state of the deprotonated retinal. The addition of a proton creates a much larger barrier implying a switching behavior of retinal that might be useful for several applications in molecular electronics. All conformations of the retinal compound absorb in the green region with small shifts following the dihedral angle rotation; however, the Schiff base of retinal (SB-retinal) at trans-conformation absorbs in the violet region. The rotation of the dihedral angle around the C11=C12 π-bond affects the absorption energy of the retinal and the binding energy of the SB-retinal with the proton at the N-Schiff; the binding energy is slightly lower at the trans-SB-retinal than at other conformations of the retinal.