Session IB

Monday, May 16th

Session IB


Strategy for Creating Modified Microarrays on Porous Silicon

Sidney G. Coombs, Sitora Khodjaniyazova, and Frank V. Bright

University at Buffalo, Department of Chemistry

Porous silicon (pSi) exhibits strong, visible photoluminescence (PL) at room temperature. One negative aspect of as-prepared, H-passivated, pSi (ap-pSi) is that the PL is unstable. The goal of our research is to stabilize the PL and simultaneously impart chemical functionality to the pSi surface through silanization with an organically modified silane. We are particularly interested in creating silane-modified microarrays on pSi which are candidates for lab-on-a-chip and simultaneous multi-analyte detection. Our previous work showed, through combined PL and Fourier transform infrared (FT-IR) imaging studies, that ap-pSi can be directly modified by contact pin-printing (CPP) organosilane arrays using a solid W pin (pin diameter, PD = 200 μm). In the case of the popular organosilane 3-aminopropyltriethoxysilane (APTES), results showed that APTES-derived spots form and rapidly spread to 5x PD after CPP on pSi. At-a-glance, this result suggests that APTES is a poor candidate for preparing microarrays on pSi where larger spots negatively impact spot density; however, spatial composition of APTES-derived spots turns out to be crucial. In this presentation, we discuss the discovery of distinct regions within APTES-derived spots on pSi and the impacts of this discovery on achievable microarray spot densities. We will demonstrate that spatially isolated APTES-modified spots and even bioconjugate spots can be prepared on pSi with as little as 2.5x PD interspot spacing.


Unraveling the Structure of Apo-metallothionein Using ESI-MS and Selective Cysteine Modification

Gordon Irvine and Prof. Martin Stillman

The University of Western Ontario

Metallothioneins (MTs) are a family of small, cysteine-rich, metal binding proteins whose major biological function is thought to be controlling zinc and copper homeostasis in addition to cadmium, lead and mercury detoxification. Able to bind up to 7 divalent metals either terminally or through bridging coordination, the structure of MT remains elusive as only the fully metalated forms have been studied by NMR and X-ray crystallography. The partially-metalated and apo forms of MT are more biologically relevant and can shed light of the mechanistic details of metal binding. In this talk, I will highlight our most recent attempts to probe the structural characteristics of apo-MTs using covalent cysteine modifications coupled with ESI-MS. Our results show previously unreported structure in metal-free MT confirmed with similar results from multiple modifying agents. This new data force us to reconsider the model of apo-MT being a fluxional peptide with no structure. We can now think of the apo-protein as being "primed" for metal binding and a loosely held globular structure.


Developing a Method Towards Assessing Si Nanostructure in Amorphous Si Agglomerates

Samantha Matthews, Joel F. Destino, and Frank V. Bright

University at Buffalo, Department of Chemistry

Crystalline Si (c-Si) plays an important role in the semiconductor industry and its crystallinity is key to product performance. As a result, quality assurance of these materials is very important.  We have assessed the nanocrystalline Si (nc-Si) homogeneity throughout amorphous Si (a-Si) agglomerates by using Raman spectroscopic mapping. We monitored the Raman band position and shape by using a peak-fitting algorithm for the transverse optical phonon mode for a-Si at 480 cm-1, nc-Si between 500 and 517 cm-1, and c-Si at 520.7 cm-1. We report preliminary findings investigating nc-Si homogeneity in these agglomerates by using atomic force microscopy, photoluminescence and Raman spectroscopic mapping.


Investigation of PBDE-47 and its Hydroxylated Analog, 5-OH-BDE-47, in Humans: Metabolic or Environmental Impact?

Deena Butryn, Michael S. Gross, Lai-Har Chi, James R. Olson, and Diana S. Aga

University at Buffalo, Department of Chemistry

Understanding sources of hydroxylated brominated diphenyl ethers (OH-BDEs) in humans has been under investigation for the past decade due to their neurotoxic and endocrine disrupting effects. There are two pathways for OH-BDEs exposure in humans, (1) metabolites of the polybrominated diphenyl ether (PBDE) flame retardants, and (2) consumption via dietary intake and occupational exposure. In vitro studies demonstrated that the most predominant PBDE congener, PBDE-47, is metabolized in the body into 5-OH-BDE-47 by the CYP2B6 enzyme. However, the activities of the allelic isoforms of CYP 2B6 (i.e. CYP2B6*1, CYP2B6*4, CYP2B6*5, CYP2B6*46 CYP2B6*7, and CYP2B6*18) vary among individuals, and can be a key insight in determining the source for the levels of 5-OH-BDE-47 in humans. The goal of this study is to quantify 5-OH-BDE-47 and PBDE-47 in blood from a cohort of 25 women from the United States. The two most common CYP 2B6 isoforms expressed were CYP2B6*1 and CYP2B6*6, and thus were compared here in relation to their PBDE-47 and 5-OH-BDE-47 concentrations. Women with the CYP2B6 *6 allele (n=8) showed good correlation between PBDE-47 and 5-OH-BDE-47 levels with an R2= 0.83, however the CYP2B6*1 allele (n= 12) showed almost no correlation (R2= 0.06) between these two congeners.  Given that the average levels of OH-BDEs in the women with the *1 and *6 alleles were not statistically different, it is evident that accumulation of OH-BDEs in humans is not solely based on biological metabolism, but also dependent on other environmental sources as well.