Table Of ContentCONTRIBUTORS
GILBERT BENZONANA
MARCELINO CEREIJIDO
D. CHAPMAN
GIUSEPPE COLACICCO
NAUM FRAIDENRAICH
PETER GOODFORD
DEMITRIOS PAPAHADJOPOULOS
LEON M. PRINCE
EMILE M. SCARPELLI
D. F. SEARS
PHILIP SEEMAN
DINESH O. SHAH
R. E. STARK
Biological Horizons
in Surface Science
Edited by
L. M. P R I N CE
Lever Brothers Company
Research Center
Edgewater, New Jersey
D. F. S E A RS
Department of Physiology
School of Medicine
Tulane University
New Orleans, Louisiana
ACADEMIC PRESS New York and London 1973
A Subsidiary of Harcourt Brace Jovanovich, Publishers
COPYRIGHT © 1973, BY ACADEMIC PRESS, INC.
ALL RIGHTS RESERVED.
NO PART OF THIS PUBLICATION MAY BE REPRODUCED OR
TRANSMITTED IN ANY FORM OR BY ANY MEANS, ELECTRONIC
OR MECHANICAL, INCLUDING PHOTOCOPY, RECORDING, OR ANY
INFORMATION STORAGE AND RETRIEVAL SYSTEM, WITHOUT
PERMISSION IN WRITING FROM THE PUBLISHER.
ACADEMIC PRESS, INC.
Ill Fifth Avenue, New York, New York 10003
United Kingdom Edition published by
ACADEMIC PRESS, INC. (LONDON) LTD.
24/28 Oval Road, London NW1
Library of Congress Cataloging in Publication Data
Main entry under title:
Biological horizons in surface science.
"A memorial to the late Professor Jack Henry
Schulman."
Includes bibliographies.
CONTENTS : Sears, D. F. and Stark, R. E. Classical
techniques of surface science.-Chapman, D. Thermal
and spectroscopic studies of membranes and membrane
components.-Shah, D. Reactions and molecular inter-
actions at interfaces, [etc.]
1. Membranes (Biology) 2. Surface chemistry.
I. Prince, Leon M., ed. II. Sears, Dewey F., ed.
III. Schulman, Jack Henry.
QH601.B48 574.8'75'015413453 72-9336
ISBN 0-12-565850-8
PRINTED IN THE UNITED STATES OF AMERICA
List of Contributors
Numbers in parentheses indicate the pages on which the authors' contributions begin.
GILBERT BENZONANA* (309), Centre National de la Recherche Scien-
tifique, Paris, France
MARCELINO CEREIJIDO (227), Department of Biophysics, CIMAE, Buenos
Aires, Argentina
D. CHAPMAN (35), Department of Chemistry, The University, Sheffield,
England
GIUSEPPE COLACICCO (247, 367), Department of Pediatrics, Albert Ein-
stein College of Medicine, Bronx, New York
NAUM FRAIDENRAICH (227), Observatorio Nacional de Fisica Cosmica,
San Miguel, Prov. Buenos Aires, Argentina
PETER GOODFORD (427), Department of Biophysics and Biochemistry,
The Wellcome Foundation, Beckenham, Kent, England
DEMITRIOS PAPAHADJOPOULOS (159), Department of Experimental Pa-
thology, Roswell Park Memorial Institute, Buffalo, New York
LEON M. PRINCE (353), Lever Brothers Company, Research Center,
Edgewater, New Jersey
EMILE M. SCARPELLI (367), Department of Pediatrics, Albert Einstein
College of Medicine, Bronx, New York
* Present address: Department of Biochemistry, University of Geneva, Geneva,
Switzerland
ix
χ List of Contributors
D. F. SEARS (1, 119), Department of Physiology, School of Medicine,
Tulane University, New Orleans, Louisiana
PHILIP SEEMAN (289), Department of Pharmacology, University of
Toronto, Toronto, Canada
DINESH O. SHAH (69), Department of Chemical Engineering and Anes-
thesiology, University of Florida, Gainesville, Florida
R. E. STARK (1), Department of Physiology, School of Medicine, Tulane
University, New Orleans, Louisiana
Preface
This book is a memorial to the late Professor Jack Henry Schulman,
whose research in surface science included studies of physicochemical,
biological, and industrial importance.
This work is directed particularly to biologists who will find many of
the techniques that have been used and the new techniques now being
developed of significance in their own research. At the same time we
wish to interest graduate students in this area of investigation. Since
many different disciplines are involved in surface science research, as
the diversity of journals in which surface phenomena are reported
demonstrates, it may be a discouraging task for an investigator to find
information relevant to his interest. This book provides introductions to
the various sources of information.
This treatise not only presents techniques used in surface science
research but experimental data as well. Physicochemical studies on
biological molecules and tissues are included. The organization of this
book is such that there is a trend to go from the more theoretical or
molecular to the more biological. Emphasis is placed on the importance
of water in determining molecular architecture and interactions. The
importance of "weak" bonds—hydrogen bonds, van der Waals attraction,
etc.—in biological phenomena is stressed at the expense of discussion
of covalent bonds of importance in biochemical or metabolic reactions.
Methods of examining molecular associations and complex formation of
molecules are discussed, and the results from such studies are reviewed.
Permeability is examined from the point of view of the energies re-
quired to penetrate between two different phases and from the role that
multicellular membranes may play in directing the diffusion of ions or
xi
xii Preface
solutes in general. Current concepts of membrane structure based on
membrane models are discussed and some new models are suggested.
Application of surface science techniques and the unique energies pres-
ent at interphases are considered in regard to drug interaction with
biological tissue and immunological phenomena. The formation of lipid
microemulsions and the transport of lipids across intestinal mucosa are
considered in two chapters, juxtaposed to emphasize this possible method
of lipid absorption. The importance of surfactant protein-lipid association
is discussed in regard to alveolar mechanics. As stated above, the role
of biochemical reactions is generally neglected to emphasize the role
of weak bonds, but the final chapter shows how important the metabolic
environment is in determining the surface structure and, conversely, how
surface structure may influence metabolism.
Different levels of scientific presentation will be found in the contri-
butions comprising this work. For example, the first chapter is meant
to be a qualitative or even "visual" discussion of the techniques of sur-
face science, where, so far as possible, words replace the precision of a
mathematical presentation. In the following chapter the reader is intro-
duced to some of the interesting and advanced techniques presently
employed in surface science research. We offer no apology for the
changes in pace; according to our experience in science, this alteration
of ease and complexity, of facts and speculation, is the nature of experi-
mentation and learning. However, to aid the reader, a table of contents
has been included at the beginning of each chapter.
The only criterion we asked the authors to meet was that they present
their concepts in a lucid manner. This they did, and we owe them our
thanks not only for making the book possible, but for making the task
of editing informative and fun. Despite the apparent tendency for
scientists to restrict their speculations, especially when writing for pub-
lication, we encouraged the. contributors to present their educated
opinions, even when these opinions were contrary to our own cherished,
but unestablished, hypotheses.
If this book can give or even suggest to its readers the stimulation
and excitement that Jack Schulman could give to his collaborators, we
will be amply rewarded.
L. M. PRINCE
D. F. SEARS
Classic Techniques of Surface Science
D. F. Sears and R. E. Stark
I. Introduction 1
A. Surface Free Energy 2
B. Total Energy Required to Form a Surface 4
C. Surface Free Energy of Solutions 5
D. Surface Characteristics 6
II. Experimental Techniques (Pure Liquids and Solutions) . .. 7
A. The Capillary Rise Method 8
B. The Falling Drop Method 9
C. The Sessile Drop Technique 11
D. Other Methods 12
III. Interpretation of the Data 12
A. Pure Liquids 12
B. Solutions of Surfactants 14
C. Derivation of the Gibbs' Adsorption Isotherm . . .. 14
IV. Experimental Techniques for Insoluble Surfactants . .. 18
A. Insoluble Monolayers 18
B. Langmuir Surface Balance 20
C. Wilhelmy Surface Balance 23
D. Experimental Results 24
E. Temperature and Pressure-Area Curves 26
F. Surface Potentials of Monolayers 27
G. Surface Viscosity 29
V. Conclusions 31
References 31
I. Introduction
Since the time of Benjamin Franklin's first observations, in 1765, of
the spreading of oil across the surface of a pond at Clapham Common,
1
2 D. F. Sears and R. E. Stark
a multitude of substances have exhibited the property of forming a
monomolecular layer on the surface of water or other liquids. Many of
these molecules with surface activity are found in biological systems
and are involved in the structure and function of these systems. Among
these molecular species are the phospholipids, steroids, and related
polycyclic compounds, many of the vitamins, porphyrins, and proteins.
Coupling the fact that such molecules are important in the function of
biological organisms with the knowledge that it is at surfaces that
molecular interactions occur, information concerning the properties of
surfaces formed by these molecules and the techniques for studying
these properties are unique and highly relevant to the solution of both
biochemical and biophysical problems.
In this chapter we shall be concerned mainly with liquids or the
liquid state of matter because biological activity and molecular inter-
actions occur in liquids. We discuss surface and interface phenomena
in a general manner as an introduction to the material in this book;
precise theoretical discussions of the material presented here are avail-
able, and references to these sources of more detailed information will
be given. The purpose is to present the subject in a fashion that will be
understandable to graduate students and to research workers who are
unfamiliar with this field.
A. Surface Free Energy
Molecules that form part of the bulk of a liquid are surrounded by
neighboring molecules in a symmetrical fashion. When a molecule
moves from the bulk phase into the surface, it loses the symmetrical
distribution of its neighbors. A surface molecule, unlike a molecule in
the bulk phase, is not subjected to the symmetrical environment of inter-
molecular attraction and repulsion. One consequence of the molecule
occupying a position in the surface is the loss of a quantitatively similar
component of molecular attraction acting normal to and away from the
surface. Thus, the surface molecules acquire a net attraction back toward
the bulk phase, which tends to minimize the surface area necessary to
encompass the volume of the liquid.
Some early investigators of surface phenomena suggested that the
tendency of liquids to reduce the surface area was a result of a region
that resembled or functioned as an elastic film around the surface of
the liquid. This film was regarded as exerting a tension, a "surface ten-
sion" in force per unit length or dynes per centimeter, which caused the
liquid to contract. This old concept of an elastic film may seem accurate
1. CLASSIC TECHNIQUES OF SURFACE SCIENCE 3
insofar as many observed phenomena are concerned. Certainly the
analogy drawn to the shrinking of a dry camel's hair brush after a dip
in water would be described adequately as an elasticlike film of water
squeezing the hairs of the brush to compress them into a fine point. How-
ever, this concept of elasticity is not valid in at least two major respects.
Unlike an elastic film, water shows no elastic limit for expansion, nor
does the energy requirement for the expansion of a water surface in-
crease as the area of the surface increases, i.e., the water has no modulus
of elasticity. The uniqueness of a liquid surface rests not in its apparent
"elasticity," but in the total energy required to bring the molecules from
the bulk phase into the surface, and in the free energy left to the mole-
cules once they are in the surface. The units for this are energy per unit
area or ergs per square centimeter, and this is numerically equal to the
units for surface tension since
(dynes/cm) X (cm/cm) = ergs/cm2
There are several experimental observations or approaches that can be
used to demonstrate the presence of the surface free energy of liquids.
The squeezing of the camel's hair brush discussed above is one. Another,
and one which has biological implications, involves different sized air
bubbles in water. Using tubes arranged as shown in Fig. 1, it is possible
to blow bubbles of different radii beneath the surface of water. Suppose
that we blow one bubble on the right with a 1-cm radius and on the
left a bubble with a 2-cm radius. Then using the appropriate stopcocks,
we cut off the air passage that was used to blow the bubbles and connect
the two bubbles, the one to the other. The question is: What will happen
and why? There are three possibilities: (1) The bubbles will maintain
the same size and shape; (2) the large bubble will cause the small
bubble to increase in size until both are the same; or (3) the small
bubble will empty into the large bubble.
It can be shown experimentally that the small bubble will empty into
the larger one, and calculations show that this is the condition that leads
to a decrease in the total air-water surface area, which means that mini-
mal surface free energy results. Taking the radii as 1 and 2 cm, respec-
FIG. 1. Arrangement for producing two air bubbles in water of unequal size
and for allowing them to bring the surface free energy to a minimum.
