Mark M. Green

New York University, New York City, NY, United States

Are you Mark M. Green?

Claim your profile

Publications (60)119.02 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Saluting the sergeant: Phg-BTA (see scheme) cooperatively self-assembles into helical aggregates and shows unprecedented racemization behavior in the presence of base. In thermodynamically controlled conditions, the addition of a small amount of chiral auxiliary to this mixture results in a deracemization reaction and a final enantiomeric excess of 32 %. A theoretical model is presented to understand in detail the results obtained.
    Angewandte Chemie International Edition 05/2012; 51(26):6426-31. · 11.34 Impact Factor
  • Source
    Filbert Totsingan, Vipul Jain, Mark M Green
    [Show abstract] [Hide abstract]
    ABSTRACT: The helix is a critical conformation exhibited by biological macromolecules and plays a key role in fundamental biological processes. Biological helical polymers exist in a single helical sense arising from the chiral effect of their primary units-for example, DNA and proteins adopt predominantly a right-handed helix conformation in response to the asymmetric conformational propensity of D-sugars and L-amino acids, respectively. In using these homochiral systems, nature blocks our observations of some fascinating aspects of the cooperativity in helical systems, although when useful for a specific purpose, "wrong" enantiomers may be incorporated in specific places. In synthetic helical systems, on the contrary, incorporation of non-racemic chirality is an additional burden, and the findings discussed in this review show that this burden may be considerably alleviated by taking advantage of the amplification of chirality, in which small chiral influences lead to large consequences. Peptide nucleic acid (PNA), which is a non-chiral synthetic DNA mimic, shows a cooperative response to a small chiral effect induced by a chiral amino acid, which is limited, however, due to the highly flexible nature of this oligomeric chimera. The lack of internal stereochemical bias is an important factor which makes PNA an ideal system to understand some cooperative features that are not directly accessible from DNA.
    Artificial DNA, PNA & XNA. 04/2012; 3(2):31-44.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Human experience informs us of the two extreme consequences of crowding: random behavior of the individuals, in which each takes a singular path; and cooperative behavior, in which the individuals in the crowd act in a predictable uniform manner, such as in a military organization These extremes find parallels in the crowded situations encountered at the molecular level, exemplified for the former by glassy states, such as often encountered in polymeric materials,1 or for the latter, in the uniform archetypal arrangements of crystals or liquid crystals. Here we review the cooperative characteristics of uniform arrangements that take a chiral form and explore how these characteristics lead to left- and right-handedness. These studies lead us to understand the basis of amplification of chirality in regular arrays, in which small influences have large consequences, and how chiral cooperativity acts in the resolution of conflict between influences favoring left- and right-handedness.2
    Israel Journal of Chemistry (Online) 11/2011; 51(10). · 2.56 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The absence of a predetermined helical sense in the polyisocyanates causes the formation of helix reversals which enforce a strong cooperativity for the amplification of chiral effects. The helix reversals though also place a limit on this amplification, a limit which would be eliminated by reducing the helix reversal population. Approaching the liquid crystal state of the polyisocyanates in both dilute and concentrated solutions appears to cause the exclusion of the helix reversals which is consistent with theoretical expectations.Since the linear birefringence of the polyisocyanate solid state precludes optical activity measurements associated with the polymer, we have synthesized hydrogen bonding side chain adapted polyisocyanates which appear by DSC and infra-red criteria to form equilibrium molecular composites with copolymers of vinyl phenol and styrene. The optical activity properties of these composites may offer a new way to probe polymer motion in the solid state.
    Macromolecular Symposia 03/2011; 101(1):363 - 370.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Helical handedness and the twist and tilt parameters of the base pairs in duplex DNA can be affected by base sequence variation and change in environmental conditions as occurs in the transformation between right-handed B-DNA and left-handed Z-DNA. For duplexes of DNA with oligonucleotide analogs such as peptide nucleic acids (PNAs), less is known about the effects on structure such as the base pair twist and tilt parameters and handedness. However, in PNA:PNA duplexes, the absence of chiral information determining helical handedness allows the relationship between preferred helical handedness and structural design to be manipulated and, therefore, better understood. In this chapter, we report a protocol for switching between B- and Z-DNA:DNA duplexes, and the experimental procedures for obtaining right- or left-handed PNA:PNA duplexes.
    Methods in molecular biology (Clifton, N.J.) 01/2011; 749:79-92. · 1.29 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Oligomers of PNA:PNA duplexes with different amino acids appended to one strand of each duplex have been synthesized and studied for their chiral optical properties. The terminal amino acid is known to affect both the handedness and amplitude of the CD signal from a given duplex. Here we have investigated an extended set of duplexes with several different amino acids appended, determining the CD, absorbance, and denaturation behavior of these chains in water and glycerol. Thermal unfolding profiles of the duplexes together with NMR data point to conformational heterogeneity as a function of amino acid, oligomer length, and solvent. The results suggest that the PNA:PNA double helix has access in solution to a dynamic ensemble of conformational states rather than a single dominant state. The conformational ensemble varies as a function of oligomer length according to the cooperative properties of the competing conformations of the double helix. A simplified statistical theoretical model allowing only two conformational states with distinct cooperative properties consistent with the denaturation results can account for much of the experimental data. This conformational heterogeneity in PNA duplexes is reflected in significantly greater flexibility of PNA:DNA duplexes relative to either DNA or RNA double helices. The results demonstrate that the principles of chiral cooperativity such as seen in the sergeants and soldiers and majority rule experiments must be altered when the structure of the system becomes a variable depending on the chiral information input.
    Macromolecules 02/2010; 43(6):2692. · 5.93 Impact Factor
  • Mark M Green, Vipul Jain
    [Show abstract] [Hide abstract]
    ABSTRACT: Strong arguments can be found in the literature addressed to the question of the origin of homochirality in life, supporting the hypothesis that primordial life could have evolved in both homochiral forms and that early on when life was still rarely found, random events led to the survival of only one of these living mirror images. This proposal is an alternative to the generally accepted view that small enantiomeric excesses of biologically important molecules were amplified to homochirality prior to life's origin. Acceptance of the possibility of "two equal runners" leads to the importance of research investigations on routes to formation of ensembles of racemic mixtures of isotactic biologically interesting polymers, supramolecular entities and aggregates.
    Origins of Life 11/2009; 40(1):111-8. · 2.05 Impact Factor
  • Mark M Green, Vipul Jain
    [Show abstract] [Hide abstract]
    ABSTRACT: Strong arguments can be found in the literature addressed to the question of the origin of homochirality in life, supporting the hypothesis that primordial life could have evolved in both homochiral forms and that early on when life was still rarely found, random events led to the survival of only one of these living mirror images. This proposal is an alternative to the generally accepted view that small enantiomeric excesses of biologically important molecules were amplified to homochirality prior to life's origin. Acceptance of the possibility of "two equal runners" leads to the importance of research investigations on routes to formation of ensembles of racemic mixtures of isotactic biologically interesting polymers, supramolecular entities and aggregates.
    Origins of Life 11/2009; 40(1):111-8. · 2.05 Impact Factor
  • Kap‐Soo Cheon, Mark M. Green
    [Show abstract] [Hide abstract]
    ABSTRACT: The signature characteristic of different kinds of polymers, synthetic and natural, is cooperativity arising from the recurring features common to all polymer structures. Cooperativity and amplification are simply different words expressing the same phenomenon leading one to expect that studies of polymers will allow small effects to be magnified, or, that is, for small effects to have surprisingly large effects on polymer properties. In the work reviewed in this short article we see this amplification at work in two different ways: (1) a synthetic polymer that forms a helical conformation but without preference for helical sense, right or left handed, is caused to take on a large excess of a single helical sense by incorporation of chiral information in surprising ways, including by forming chiral centers by deuterium substitution; (2) two polymers that mix homogeneously with each other by virtue of an unknown attractive interaction are revealed by deuterium labeling to be involved in a weak hydrogen bond between a hydrogen bound to aromatic carbon and an ethereal oxygen. Copyright © 2007 John Wiley & Sons, Ltd.
    Journal of Labelled Compounds 08/2007; 50(11‐12):961 - 966.
  • Sonit Tomar, Mark M Green, Loren A Day
    [Show abstract] [Hide abstract]
    ABSTRACT: Although all filamentous phages are constructed of chiral components, this study of eight of these phages (fd, IKe, I(2)2, X-2, Pf1, Pf3, tf-1, and X) shows that some form nematic liquid crystals, which are apparently oblivious to the chirality of the components, while others form cholesteric liquid crystals revealing a type of structural chirality not normally encountered. Additions of dopants that interact with the DNA or protein components of the viruses change the liquid crystal properties of seven of the phages. In these seven, DNA-capsid symmetry differences do not allow strict structural equivalency among the protein subunits. The polymorphism arising from this nonequivalency is proposed here to give rise to coiling of the filaments, a large-length-scale chirality that is responsible for forming cholesteric liquid crystal phases. Only one phage of those studied here, Pf1, which is distinguished from the others in its DNA-capsid interactions, forms nematic phases under all conditions tried. The formation of liquid crystals has been developed as a method to detect subtle overall shape effects arising from DNA-subunit-derived polymorphism, an unusual role for the mesogenic state and a new tool for the study of filamentous phage structure.
    Journal of the American Chemical Society 04/2007; 129(11):3367-75. · 10.68 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A bicopper complex was prepared with chiral ligands. The self-assembly of the complex in trans-decalin differed greatly for the racemic and nonracemic ligands. With the latter the resulting gel formed at a lower concentration and exhibited a higher thermal transition temperature. A large optical activity was found in the nonracemic bicopper complex, which was used to probe the process of filament formation, i.e., the aggregation-dissociation process. The material with nonracemic ligands may form a longer nanoscopic filament.
    Chirality 12/2004; 16(9):661-4. · 1.72 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The titration of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMA) with LiOCH3 and NaOCH3 in methanol was studied by solution viscosity, potentiometry, and NMR spectroscopy. When titrating with LiOCH3, the reduced viscosity (rv) first increased with an increasing degree of neutralization (α) but then decreased due to counterion condensation and the mutual attraction of the ion-pair dipoles. The earlier rv maximum and the steeper rv decline in the case of PMA were attributed to a lower local dielectric constant. The rise of the pK with α continued for PAA even after the onset of counterion condensation as judged by the rv reversal, although Manning's theory predicts that the polymer charge density should remain constant. The NMR spectra of PMA and PAA showed a significantly greater line broadening with increasing neutralization in methanol than in D2O, indicating a sharp decrease of conformational mobility due to the energetic interactions between the polymer-bound ionic charges and ion-pair dipoles in the medium of low dielectric constant. When PAA or PMA was titrated with NaOCH3, where the two polymers showed a similar behavior, the collapse of the polymer chain (as evidenced from both rv and NMR intensity) occurred at a much lower α than with lithium methoxide titration, and led to a rv much lower than that of the two unneutralized polymers. This was attributed to a much stronger tendency of Na ion-pairs than Li ion-pairs to dimerize.
    Macromolecules. 10/2004; 37(23).
  • Mark M. Green, Shneior Lifson, Akio Teramoto
    [Show abstract] [Hide abstract]
    ABSTRACT: In contrast to random coil polymers, polyisocyanates maintain a highly extended helical conformation in solution. This structural characteristic causes unusually large chiral optical properties to arise from copolymerization of tiny proportions of optically active monomer isocyanates with achiral isocyanates or even from stereospecific placement of deuterium in the side chain of poly(n-hexyl isocyanate). These effects can be understood as phenomenologically related to the optical activity amplification properties of vinyl polymers studied by Pino and his co-workers and ascribed to breaking the energetic degeneracy of the otherwise equally populated left- and right-handed helical states of the backbone. Statistical thermodynamic calculations, based on this model, and analogous to those carried out earlier on the vinyl polymers, allow matching the temperature and molecular weight dependence of the optical activity in poly((R)-1-deuterio-1-hexyl isocyanate) to the approximate responsible energy terms.
    Chirality 09/2004; 3(4):285 - 291. · 1.72 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Studies of copolymers of chiral and achiral units forming a helical array correlate to statistical physical predictions of the influence of the chiral units on the helical sense taken by the array. In the absence of conflict among the chiral units for helical sense control, the sergeants and soldiers experiment, a larger chiral bias leads to increased control. However, when conflict exists among the chiral units for helical sense control, the majority rule experiment, a larger chiral bias leads to decreased control of the helical sense and therefore a smaller optical activity. Changing the achiral units in the majority rule experiment can change the nature of the statistical physics between statistical and thermal randomness. In general, the experiments quantitatively demonstrate that the effect of chirality is not an intrinsic property of the chiral moiety but rather depends on the molecular environment. Copyright © 2004 John Wiley & Sons, Ltd.
    Journal of Physical Organic Chemistry 07/2004; 17(9):719 - 723. · 1.58 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The magnetic properties and the nucleation capability of a self-assembling bicopper complex are reported. Attention is focused on the effect of the chirality of the bicopper complex. Comparison is made between the racemic mixture and the right-handed enantiomer.
    Macromolecular Symposia 11/2003; 203(1):265 - 270.
  • Frontiers in Optics; 10/2003
  • [Show abstract] [Hide abstract]
    ABSTRACT: We describe two different ways of encapsulating within the fibrils of thermoreversible polymer gels the filaments of a supermolecular polymer formed by self-assembly of a bicopper complex. Heterogeneous nucleation is brought about with gels made from isotactic poly(styrene) while compound formation occurs with gels made from poly(hexyl isocyanate). These ways depend upon the interaction between the wings of the supermolecular polymer and the side groups of the polymer. In all cases, the filaments retain their 1-D structure. Preliminary results from magnetic susceptibility measurements show a striking difference between the pure and the encapsulated supermolecular polymer.
    Macromolecular Symposia 09/2003; 200(1):9 - 20.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Helical polymers appended with paired structurally different enantiomers, which have opposing helical sense preferences, yield a new kind of relationship between optical activity and temperature, and also reveal unusual details of the nature of chiral interactions. Consistent with a statistical physical theory developed for these experiments, the proportion of the competing chiral groups, determined by synthesis, fixes the compensation temperature at which the helical senses are equally populated. The lyotropic liquid crystal state formed by these polymers yields therefore a nematic state at any chosen temperature over a very wide range, with a cholesteric state arising with tightening pitch as temperature deviates from this point. Far from the nematic temperature, the pitch reaches the nanometer scale and therefore the reflection of visible light. Before crossing zero at the nematic temperature, the optical activity becomes so large that it may be observed with the unaided eye through crossed polarizers.
    Journal of the American Chemical Society 07/2003; 125(24):7313-23. · 10.68 Impact Factor
  • Mark M. Green
    Biopolymers 01/2003; 68(3):277-277. · 2.88 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Time-resolved electron spin resonance (TR-ESR) has been used to investigate the effect of pH-dependent poly(methacrylic acid) clustering on the radical pair generated from photolysis of a poly(methacrylic acid) acid sample randomly labeled with the common α-hydroxy ketone photoinitiator 1. The TR-ESR spectra for the ketyl radical show a dramatic change in electron spin polarization mechanism, from a predominantly triplet mechanism (TM) at low pH (below 6) to a predominantly radical pair mechanism (RPM) at high pH (above 7). The ratio of RPM/TM polarization exhibits a sigmoidal behavior as a function of pH which passes through an inflection point at pH 6.9 ± 0.1. The inflection point agrees well with previous estimates for pH-dependent cluster opening in poly(methacrylic acid). These results indicate that the pH-dependent cluster is capable of forming a cage around the geminate radical pair which restricts its motion at low pH. At higher pH, the cluster opens, allowing the ketyl radical to escape the pair. Studies of the benzoyl partner in the radical pair, which is attached covalently to the polymer backbone, indicate differing environments within the cluster even at pH below cluster opening. This study represents the first application of TR-ESR and electron spin polarization (ESP) to the problem of pH-dependent clustering and reveals new features of the pH-dependent poly(methacrylic acid) cluster.
    Macromolecules 10/2002; 35(24). · 5.93 Impact Factor

Publication Stats

321 Citations
119.02 Total Impact Points

Institutions

  • 2012
    • New York University
      • Department of Chemistry
      New York City, NY, United States
  • 2004–2012
    • Polytechnic Institute of New York University
      Brooklyn, New York, United States
  • 1994–2007
    • Polytechnic University of Bucharest
      Bucureşti, Bucureşti, Romania
  • 2003
    • City University of New York - Brooklyn College
      Brooklyn, New York, United States