Violent attacks on Middle Easterners in the United States during the month following the September 11, 2001 terrorist attacks

OBJECTIVES

To document and describe hate related violent attacks on Middle Easterners or those perceived to be Middle Easterners during the month following the September 11, 2001 terrorist attacks in New York City and Washington, DC.

METHODS

The LexisNexis database of newspaper reports were used to identify incidents of hate related violent acts against Middle Easterners or those perceived to be Middle Easterners in the US between September 1 and October 11, 2001. A total of 100 incidents of hate related violence were identified in the 2659 news articles that were reviewed.

RESULTS

Of the 100 incidents of violent victimization that took place during the period September 1 to October 11, only one incident occurred before September 11. The 99 incidents that occurred after September 11 involved at least 128 victims and 171 perpetrators. Most violent victimizations occurred within 10 days of the attacks, involved male perpetrators and male victims, and occurred in convenience stores, on the streets, at gas stations, at schools/colleges, and at places of worship.

DISCUSSION

Most violent victimizations occurred in the 10 days immediately following the terrorist attacks indicating that interventions that promote tolerance and understanding of diversity need to be implemented quickly in order to be effective. In addition, patrolling by police and Neighborhood Watch programs around convenience stores and gas stations may also be effective strategies for reducing hate related violent crimes.

Asymmetric DNA binding by a homodimeric bHLH protein

Protein-DNA interactions that lie outside of the core recognition sequence for the Drosophila bHLH transcription factor Deadpan (Dpn) were investigated using minor groove binding pyrrole-imidazole polyamides. Electrophoretic mobility shift assays and DNase I footprinting demonstrate that hairpin polyamides bound immediately upstream, but not immediately downstream of the Dpn homodimer selectively inhibit protein-DNA complex formation. Mutation of the Dpn consensus binding site from the asymmetric sequence 5'-CACGCG-3' to the palindromic sequence 5'-CACGTG-3' abolishes asymmetric inhibition. A Dpn mutant containing the unnatural amino acid norleucine in place of lysine at position 80 in the bHLH loop region is not inhibited by the polyamide, suggesting that the epsilon amino group at this position is responsible for DNA contacts outside the major groove. We conclude that the nonpalindromic Dpn recognition site imparts binding asymmetry by providing unique contacts to the basic region of each monomer in the bHLH homodimer.

Rapid identification of key amino-acid-DNA contacts through combinatorial peptide synthesis

BACKGROUND

Basic helix-loop-helix (bHLH) transcription factors are characterized by a conserved four-helix bundle that recognizes a specific hexanucleotide DNA sequence in the major groove. Previous studies have shown that amino acids in the basic region make base-specific contacts, whereas the HLH region is responsible for dimerization. Structural data suggest that portions of the loop region may be proximal to the DNA; however, the role of the loop in DNA-binding affinity and specificity has not been investigated.

RESULTS

Protein-DNA recognition by the Drosophila bHLH transcription factor Deadpan was probed using combinatorial solid-phase peptide synthesis methods. A series of bHLH peptide libraries that modulate amino acid content and length in the loop region was screened with DNA and peptide affinity columns, and analyzed using matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). A functional bHLH peptide with reduced loop length was found, and Lys80 was unambiguously identified as the sole loop residue critical for DNA binding. Unnatural amino acids were substituted at this position to assess contributions of the terminal amino group and the alkyl chain length to DNA-binding affinity and specificity.

CONCLUSIONS

Using combinatorial solid-phase peptide synthesis methods and MALDI-MS, we were able to rapidly identify a key amino acid involved in DNA binding by a bHLH protein. Our approach provides a powerful alternative to current recombinant DNA methods to identify and probe the energetics of protein-DNA interactions.

Effects of taurine on human embryo development in vitro

Glutamine and taurine are reported to be beneficial for mouse embryo development in vitro, and we have recently shown that glutamine improves human blastocyst formation in vitro. This randomized study compared the development of supernumerary human embryos in the presence of 1 mmol/l glutamine and/or 5 mmol/l taurine from the 2-4-cell stage to the blastocyst stage. Blastocyst development and cell numbers were similar in the presence of glutamine or taurine: 52.6% and 58.3% of the embryos reached the blastocyst stage, respectively. Pyruvate uptake was similar in the presence of glutamine or taurine throughout development, as was lactate production after the 8-cell stage. Before this stage, lactate production was 4-fold higher in the presence of taurine (P < 0.001). The proportion of embryos reaching the blastocyst stage was similar with glutamine alone or with glutamine and taurine (62.5% and 47.2% respectively), as were the blastocyst cell numbers (63.0 +/- 4.6 and 61.0 +/- 5.1 respectively). In conclusion, taurine supports development of 2-4-cell human embryos to the blastocyst stage, although it does not further augment the beneficial effects of glutamine.

Characterization of the DNA binding properties of the bHLH domain of Deadpan to single and tandem sites

The basic helix-loop-helix domain of the Drosophila transcription factor Deadpan (Dpn) was prepared by total chemical protein synthesis in order to characterize its DNA binding properties. Circular dichroism spectroscopy was used to correlate structural changes in Dpn with physiologically relevant monovalent (KCl) and divalent (MgCl2) cation concentrations. In addition, we have used electrophoretic mobility shift assay (EMSA) and fluorescence anisotropy methods to determine equilibrium dissociation constants for the interaction of Dpn with two biologically relevant promoters involved in neural development and sex determination pathways. In this study, we have optimized DNA binding conditions for Dpn, and we have found a markedly higher DNA binding affinity for Dpn than reported for other bHLH domain transcription factors. Dpn binds as a homodimer (Kd = 2.6 nM) to double-stranded oligonucleotides containing the binding site CACGCG. In addition, we found that Dpn bound with the same affinity to a single or tandem binding site, indicating no cooperativity between adjacent DNA-bound Dpn dimers. DNA binding was also monitored as a function of physiologically relevant KCl and MgCl2 concentrations, and we found that this activity was significantly different in the presence and absence of the nonspecific competitor poly(dI-dC). Moreover, Dpn displayed moderate sequence selectivity, exhibiting a 100-fold higher binding affinity for specific DNA than for poly(dI-dC). This study constitutes the first detailed biophysical characterization of the DNA binding properties of a bHLH protein.

Mass spectrometry as a readout of protein structure and function

Proteins have evolved to carry out very specific functions within the cell by interacting with a diverse set of biomolecules. Understanding how a protein's higher order structure relates to its function is important for defining the molecular basis of these interactions. In recent years, mass spectrometry has become an important tool for dissecting protein structure and function. Using electrospray ionization (ESI)- and matrix-assisted laser desorption/ionization (MALDI)-based approaches, it has been possible to monitor protein folding, characterize noncovalent protein complexes, and assess the contribution of individual amino acid residues to a protein's function. Here, it is our goal to summarize these approaches and highlight recent, biologically relevant applications where mass spectrometry has provided unique insight into the mysteries of protein structure and function.

Characterization and charge distribution of the asparagine-linked oligosaccharides on secreted mouse thyrotropin and free alpha-subunits

Mouse hemipituitaries in vitro secrete TSH, composed of an alpha-beta heterodimer, as well as excess (free) alpha-subunits. By dual metabolic labeling with [35S]sulfate and [3H]mannose, we have characterized oligosaccharides from secreted TSH alpha, TSH beta, and free alpha-subunits released from the apoprotein by enzymatic deglycosylation. Oligosaccharides from each subunit displayed a distinct anion exchange HPLC profile due to a specific pattern of sialylation and sulfation. Six species were obtained from TSH alpha (with two glycosylation sites), including neutral oligosaccharides as well as those with one or two negative charges. For TSH beta (with one glycosylation site) at least eight oligosaccharide species were noted, representing nearly every permutation of sialylation and sulfation; approximately 30% contained three or more negative charges. Analysis of [3H]mannose-labeled oligosaccharides on Concanavalin-A-agarose showed 85% binding for those from TSH alpha, 70% for free alpha, and 50% for those from TSH beta. These data demonstrate that oligosaccharides from secreted TSH beta were more sialylated and sulfated, consistent with a more complex branching pattern, than those from TSH alpha. Oligosaccharides from free alpha-subunit were more sialylated than those from TSH alpha, and the net negative charge was intermediate between those of TSH alpha and TSH beta. Although great microheterogeneity is present even at the single glycosylation site on the beta-subunit of secreted TSH, a pattern of sialylation and sulfation could be discerned. If one assigns probabilities of sialylation [p(N)] and sulfation [p(S)] based on the observed distribution within monoacidic (charge -1) species, the proportion of diacidic (charge -2) oligosaccharides could be predicted for each subunit by [p(N)]2, 2[p(N)] [p(S)], [p(S)]2, corresponding to species containing two sialic acid, one sialic acid and one sulfate, and two sulfate residues, respectively. This suggests that the probability of sialylation or sulfation at a second site on these oligosaccharides is similar to that at the first and that anionic oligosaccharides in secreted TSH and free alpha are distributed binomially with regard to sialic acid and sulfate residues.